Hi folks, thanks to all of you for responding. Sorry to be so late to acknowledge, been offline over the weekend.
whs, I don't have any imaging or backup programs in use, so it's something else.
This only started a short while back when I started using the drive on my new Vista laptop, and I thought it was caused by the Vista explorer Search Indexing service, but the refusal to eject is happening on my XP desktop as well.
I also considered that it might be my anti-virus running an active scan. I have Macaffee on my Dell Vista laptop, and Norton's on the XP desktop. I'm kicking both of them to the curb this week, and install Avast on both machines. (no internet connection, so I don't need such elaborate suites.)
Just Logging Off and back on doesn't work, I have to actually reboot to get it to turn loose.
ScottW, thanks for the link, I will give that tool a try and see if I can identify the culprit, and report back my results.