Re: X freezes with FX5200
AGP support is one frequent cause of crashes. Disabling it (option 0) or switching to agpgart mode (option 2) is worth a try. To your device section try adding one of the following:
Option "NvAGP" "0"
(Disabled, more likely to work but slower graphics performance)
Option "NvAGP" "2"
(agpgart, Less likely to work but still worth a try due to the faster graphics performance)
I suggest trying option 0 first and option 2 if that fixes the problem.
Also you may want to try getting the latest BIOS from Asus if the configuration change doesn't help.
For me agpgart works with the 2.6.4 kernel in SuSE 9.1 and the same model of motherboard you have (A7V8X-X). I have not needed to upgrade my BIOS.
Also, I have an FX5200 board but for BoardName I have "0x0322". I think the 0x board names may vary within a model due to AGP speed, Video RAM size, or something like that, but I'm not sure.