USB problem after upgrade

Archived from groups: microsoft.public.win2000.setup_upgrade (More info?)

After upgrading Windows 2000 from SP3 to SP4, including
the security fixes etc that the Windows Update website
provides, I'm having trouble with my USB disk (Maxtor
OneTouch, connected via USB2.0).
The Device Manager reports that everything's fine (except
some IRQ channels being shared by multiple devices), but
sometimes I'm unable to write files to the disk (the fopen
() call in C fails). The problem isn't the disk (I've
tested it and I'm experiencing the same problem on 2
different PCs with different disks), so the problem must
be the USB communication with the device.
I've tried lots of things (like uninstalling Maxtor's
drivers to use standard Windows driver usbstor.sys), but
the problem still exists. How can the upgrade from SP3 to
SP4 have such an impact? I know that the USB support
changed between those service packs, but I don't see how
it can affect my disk's performance. The device (using
USB2.0) seems to be working just fine.

Please help me find the problem/solution! This is an
urgent problem!

Thanks in advance

Tim