I assume the console had this in red:
Exception in thread "main"
and the error message was a pop-up that read as you have said.
The problem is that the builder does NOT like directories with spaces in its name. If your workspace is "c:\Documents and Settings\eclipseworkspace" the builder will not run and the error will pop up.
Your workspace directory should be something WITHOUT SPACES. That should fix your problem.
- Rob Stryker
JBoss AOP IDE
I tried and it works.