You will only see a red-x error on your project ... but none of the files are showing they contain an error. So ...
Google led me here
And I found the following to be my root issue ...
[2010-08-27 15:32:04 – (Project Name)] Error generating final archive: Debug certificate expired on 7/30/10 10:42 PM!
After searching I found this link which suggests the solution: http://www.androidian.de/?p=940.
The problem comes from the fact that Android required the applications to be signed even in the debug mode. So it uses a keystore file called debug.keystore to providde keys for signing applications in debug mode. This key store file has a validity period by default 365 days from its creation date.
This is the site that I followed to fix