I had to recreate one of my Eclipse workspace again. Last time, it was because Sysdeo plugin was acting strange. This time, it was the IDE itself getting confused (either JDT Core or UI module). As usual I used QuickFix to import a class I referenced but the class still could not be resolved. When I rebuilt the project using an Ant file, everything compiles perfectly which confirms that it was a JDT bug. But my rebuilding of the project made JDT recheck all the classes and, since it was confused about the class I imported, it marked all the classes that used the imported class as having errors.
This would have been bearable if the confusion got cleared up on restarting the IDE. Nope. For some strange reason, the IDE persisted this confusion into the workspace. So I rebuilt the workspace and the problem went away. Sheesh. I'll bet 3.0.1 will be released sooner than the scheduled September time frame.