unable to stop USB device

[Van]

I have Win XP home on one computer, and XP Pro on the
other. I recently added a USB2 card to the desktop, and
a USB2 PCMCIA card to the laptop. Everything works fine
using an external USB2 hard drive until I go to
disconnect the external hard drive. On both machines I
usually (but not always) get a cryptic message
sayting "The device 'Generic volume' cannot be stopped
right now. Try stopping the device again later."

Anyone else out there having a similar problem? Any
solutions?

Thanks in advance.

Van