That AGP Texture issue is a problem, though, and may very well be contributing to your freezes and lockups. I'd be concentrating on that.
I have seen other people with some problems with this motherboard. Some workarounds, but no absolute "this is the fix for all" deals.
Ok, first: Make sure you don't have the Asus Probe software running when you play games. This can cause stuttering and freezing.
Secondly, the AGP texture problem. This is a big one, and can cause you all manner of issues.
You've already installed the Hyperion 4-in-1's (4.51, right?). Reinstall the Catalyst drivers. Reinstall DirectX 9b.
See if you've got AGP texture acceleration.
DirectX 9.0b download:
Download it here
Reboot after installing DirectX, of course. Check dxdiag to see if you've got AGP texture acceleration. If so, play some games.
One guy got his AGP texturing to work by changing some bios settings in the AGP section:
"Memory Frequency set to AUTO I changed it to 266
Video Memory Cache Mode was set to UC changed it to USWC
AGP Performance was disabled set it to ENABLED
AGP Fast Write Control was disabled set it to ENABLED
Graphics Aperature is still set to 128
AGP Capability still set to 4x Mode"
(these may or may not work for you; just make a note of your current settings so you can change them back if need be)