Eclipse will not compile

Hi everyone, I am experiencing allot of difficulty running my programs with Eclipse, I have the latest updates on Eclipse and SDK and my program does not have any errors. Yet, when I try to run/compile the program, it says "Your project contains errors, please fix them..." and there is no indication of what the error might be which makes sense since it was not able to compile.

This has happened to me several times, the only solution I have come up with is to start a new program, copy in the code bit by bit (ha ha) make sure it runs at intermediate steps until I have all the functionality back and the program is running.

This occurs very unpredictably, I have a program running, I make a change and the error occurs, I put the code back exactly how it was and it won't run. Very frustrating.

Any ideas?

Thanks,

Jacques