Abit GeForce4MX with Asus P3V4X locks up with AGP x4 enabled

[Radders]

I have just installed an Abit GeForce4 MX on a dual boot system with relatively clean installs of WindowsME and XP Pro. With either OS running some games (particularly those based on the Unreal engine) causes the machine to lock up. If I install the 4in1 drivers with the AGP driver in normal mode on Millennium everything works ok but I think it is only using x2 AGP. With XP I can only get things working if I use the Geforce tweak utility and drop it down to AGP x1

My PC specs are:
PIII 800EB (using a slocket adapter)
Asus P3V4X motherboard
256Mb PC133 (2x 128Mb)
Abit GeForce4 MX