I have a package com.foo in my source folder. In that package is a class SomeClass.
I have a class AnotherClass in com.bar that declares a SomeClass.
After starting a saros session with two other co-workers, on all three of our machines SomeClass is not recognized by AnotherClass. We are of course importing com.foo.SomeClass and that class was (naturally) recognized by eclipse before we started the session.
A co-worked solved the problem as I was writing the question. Somehow the Order and Export tab in the Java Build Path window had all of our project resources selected including external libraries. We simply deselected all resources except for the source folder and built the project.
You can get to the Java Build Path window by right clicking the src folder in the package explorer and going to Build Path > Configure Build Path…