Question

I have updated my packages using Android SDK Manager and clicked on Help > Check for updates and updated installed plug-ins. I was prompted to restart eclipse, and now after restarting,

I get following Error code

'Building workspace' has encountered a problem.
Errors occurred during the build

Errors occurred during the build.
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ResourceManagerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.PreCompilerBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PreCompilerBuilder.
Bad version number in .class file
Error instantiating builder 'com.android.ide.eclipse.adt.ApkBuilder'.
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file
Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.
Bad version number in .class file

Answer 1

You sure to have the correct dependencies? Which eclipse version do you have installed? Which JRE/JDK is used to run eclipse with?

Bad version number means that there is a mismatch between the intended target java version and the one you use (see here).