Error has eccurred in Eclipse during importing class

Question

I am working on Spring MVC project in Eclipse Juno. I have a few packages with my classes. Once I have used one class in another from different package I have occured this error in pop-up message:

An error has occurred. See error log for more details.
assertion failed: 

And there is not nothing more informations. What should I do in Eclipse to prevent such errors?

Answer 1

First read about What is assertion.
And looks like assertions are enabled try to run program after disabling it.