I'm on Windows 8x64.  I've only had success mining with  13.1; 13.2; 13.3.  Otherwise, 13.4 and 13.6 cause me to get  "check hardware" errors with guiminer, and cgminer simply crashes.

Here's what I do. I use driver fusion to scrap "everything" and start fresh.  I install SDK 2.6 (a stand alone package).  Next I install my catalyst 13.3, and I'm successful. Did the same thing with 13.4 an 6 this time, no success.. Something has changed and it's a bad thing for bitcoin miners.

Here's what I noticed, if I install cat 13.3 as is, it fails to mine.  I MUST install the SDK 2.6 package first before the cat drivers.  Did cat 13.4 and 6 alone as well, then tried it with SDK 2.6 with no results.  It looks very bad for us.