I'm getting the same problems as other people on WinXP Pro. What this guy says at Amazon is right:
I have used UMAX scanners since 1996 (the 1220S and 2100U) and had fairly good luck with them until recently. UMAX customer support has always been pretty much non-existent but their scanners had a good following so one could always find a solution to their screwy driver problems if one looked around on the web. With the advent of Windows XP however, you might as well throw your UMAX gear away. Their parallel port scanners are not supported at all and the SCSI and USB scanners are supported only if you buy the new drivers at a cost of [money amount]. What is worse is that the XP drivers that they sell you don't work at all. Don't get sucked in!! UMAX is trying to rip you off by selling you driver software that won't install and they do not provide any useful support once you paid the money.
So, don't buy UMAX. The [money amount] is $14.50, by the way.
I have an old UMAX S12 (I think?) that still works under Win2k with the SCSI driver... but it's an old honking SCSI scanner and just takes up too much room on the desk.
For day-to-day use (which isn't that frequent, actually) I have a cheapo Cannon CanoScan, and it gets the job done. If I was doing more scanning more often I'd probably wish it had a larger scanning area though, for things like old Life magazine covers.