I'm having the same problem, too - uninstalled and reinstalled Catalyst drivers, AMD Stream 2.4, and a new install of guiminer, and it *still* won't work. 
Earlier today I updated guiminer by extracting python 1.5 overwriting 1.4, but guiminer still worked after that.  Later today, it stopped working, and I have no idea why, especially after this clean install.

I also have this problem - no results when searching google, either.    I did try out Phoenix 1.5 today, by copying the new version into the guiminer folder, so I thought that may have done it, but I set up a fresh copy of guiminer 6/14/11 version, and it still won't work >_< 
Need some help please.