XPe problems with 91.33 and 91.31

I have run into a problem with the 9x.xx nVidia drivers using a
GeForce7300GS PCI-x card - my DirectX application fails when it calls
GetDeviceCaps() with D3DERR_NOTAVAILABLE. This is the same error which
is returned if no driver is installed at all. If I simply replace the
nv4_disp.dll and nv4_mini.sys files with ones from an 8x.xx series
driver, the call succeeds.

I can recreate the problem under XP Pro if I install the driver, but
attempt to run the application _without_ rebooting. After rebooting,
the call succeeds. Any ideas? This never occurred before the 9x.xx
series. I am looking into post-reboot registry changes now, but any
help would be much appreciated.

Thanks,

Jason