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.
I'm using guiminer on Windows8 x64 too
I installed the 13.6 drivers with SDK 2.
8 - works ok with my 7950, but can't connect at all with my GTS 450