It's a pretty vague error... looking at the changes I made I can't figure out what could cause that. You say it worked on the last guiminer? One thing you could try is deleting your miners and creating new miners just to see if that does anything.

Another thing you could try is to run poclbm from the command line and see if that works correctly, in case there was an issue with the latest poclbm. If you look in the console when you start tup you can see the command to use, something like:

poclbm.exe kiv:pass@localhost:8332 --device=1 --platform=0 --verbose -r1

Hey everyone, a new version of the miner is available from the download link on the first post or here:

guiminer-20121118.exe (self-extracting archive)    

The main point of this update is to get the latest poclbm version including Stratum support.

I removed support for the old Phoenix since I didn't have time to get GUIMiner working with the latest Phoenix 2; so if you're happily mining on old Phoenix then you don't need this release

As always donations are appreciated; my address remains the same at 1MDDh2h4cAZDafgc94mr9q95dhRYcJbNQo. While I still love Bitcoin I'm not mining any more myself and am really busy in my personal life, so this release is purely for the benefit of you guys, the community.

If anyone has issues please report them in this thread or PM and I'll try to help out. Cheers!

GUIMiner development is stopped? There were several updates for miners since february but GUIMiner is not updated,
which means anyone using latest version of it actualy uses quite outdated versions of miners that come in package.