I'm using an Abit BH6 which uses the 440BX Intel chipset, so its not a chipset problem.
I talked today with a tech from Creative and he told me that this problem is a bug that's been present in the Nvidia drivers since 5.22. He says that it will probably be fixed in the next revision, although he didn't say who's revision, CL's or Nvidia's. I have the feeling that whatever the bug is, it isn't removed by standard uninstallation procedures, since downgrading doesn't seem to help, except for the first instance of a reinstall before a reboot, where it works for a bit.
As far as you, Cuke, did you ever install 5.22? I think that 5.25 and 5.30 don't have the bug, but also don't remove it if you are upgrading from a 5.22 installation.
The guy from CL did say that they've been hearing a lot about this one, and that they should be fixing it real soon. I won't be holding my breath.