Can't install printer/scanner on USB

I have been unable to install an HP PSC 1210. As soon as
the USB cable is plugged in or the PSC is switched on I
get the message "Cmdninst has caused an error in
USER.EXE". Neither the USB ports on the mainboard (GA
6VX7-4X) or a PCI card (EIO USB2.0) will work. I have
updated the BIOS and VIA drivers - no change. HP support
has been useless. It won't install in safe mode either.
The device manager does show power at 2mA when it's
plugged in, but that is the only sign of life. Any ideas,
before I tear out the last of my hair?
Allan