http://www.3dfxgamers.com/view.asp?IOID=1878 
In the banshee.inf file the memory clock setting
is set to 110 Mhz by
default. This setting can cause desktop lockup problems. I have found that
changing this setting to 100 instead of 110 fixes the lockup problem.
here is the section from the inf file
OLD INF section
[banshee_SoftwareDeviceSettings]
HKR,, InstalledDisplayDrivers, %REG_MULTI_SZ%, banshee
HKR,, VgaCompatible, %REG_DWORD%, 0
HKR,, UseNonBIOSModeSet, %REG_DWORD%, 1
HKR,, memclocking, %REG_DWORD%, 110
NEW inf section
[banshee_SoftwareDeviceSettings]
HKR,, InstalledDisplayDrivers, %REG_MULTI_SZ%, banshee
HKR,, VgaCompatible, %REG_DWORD%, 0
HKR,, UseNonBIOSModeSet, %REG_DWORD%, 1
HKR,, memclocking, %REG_DWORD%, 100
This one change can fix the desktop lockup problem.