I have updated my Ubuntu box to 11.10 and then Eclipse also have been updated to 3.7.0 Indigo with CDT 8.0.1
Then the following problem occurs:

I have included the vector header file but the compiler said that Symbol 'vector' could not be resolved. I also defined #define int Comparable, but Eclipse also said Symbol 'Comparable' could not be resolved and so on….
Although lots of errors occur, compiling was finished successfully!
I have tried to use g++ to compile the code, it had no problem.
Time after time a crash of Eclipse, the VM or the computer or even just long months of development start to wear down the stability of the workspace where Eclipse stores everything.
Check the
<workspace dir>\.metadatadirectory to get an idea of just how much Eclipse generates and stores in your workspace. Every time you add a plugin, upgrade a plugin, remove a plugin that puts and changes information in your workspace.A proof is that this issue usually comes just after upgrading Eclipse. (In my case to Indigo).
The easiest way to fix up a dusty workspace is using the
-cleancommand line argument to the eclipse.exe executable.Eclipse help docs tell us what this command does:
There are three ways one can use the
-cleancommand line argument:-cleanargument.The advantage of step 3 is you can keep the script around and use it each time you want to clean out the workspace.
This page solved the problem to me!Hope it can help everybody else.