Android project not compiling, error in build path?

I wasn't really sure how to title this, but basically I am having an issue with something in my android build path or something. I have 2 projects, one of which worked before, and I haven't touched in since and now it won't compile either. Both projects just have an x on the 开发者_如何学Cfolder saying there is an error in them somewhere, but none of the java files have errors flagged, and neither does the r.java. I figured someone might have had a similar problem and could point me in the right direction.

Thanks in advance.

WWaldo

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Try: clean project in Eclipse or refresh project or both. If still doesn't work, restart Eclipse.

edited:
Answer for your problem with debug certificate:
"Debug certificate expired" error in Eclipse Android plugins

And probably answer for missing gen and R.java file:
R cannot be resolved - Android error