I would recommend sticking with the old versions of ATI drivers. Also, if you are mining 24/7 with a dedicated machine, you should probably use cgminer vs. GuiMiner as cgminer is much more stable.
I'm not mining 24/7 and I use the comp for other things so I went with GUIminer for ease of use. So with cgminer you have to compile it yourself, there's no already compiled DL available or anything?