Weird XP shutdown problem with USB drive

[Rampage]

I just purchased an external Western Digital 80 gig USB hard drive strictly for purposes of having a reliable data backup. I'm on XP Pro SP2, XP2000+ processor, 1 gig of RAM, Asus A7V333 motherboard with BIOS revision 1.017. The drive is hooked up to a USB 2.0 port and has it's own power switch.

If I have the USB drive turned on during any given session, I can't get the system to shut down regardless of if the drive is turned off or on when I issue a shut down (or restart) command. I've tried the following:
used "safely remove hardware" tool
turned off "System Restore" monitoring of this drive
verified there aren't any options set to suspend power
combed the Microsoft knowledge base for shut down problems
contacted WD tech support, which didn't help

There is plenty more I can try, but I was wondering if anyone had seen this type of behavior before? If the drive never gets powered on, there are no shutdown problems. I have the drive partitioned into 1 very small FAT32 partition and another partition that my backup application uses for storage of images. I have waited as much as 5 minutes after seeing the "Windows is shutting down" message before resetting (normal shutdown time is about 10 secs.). There are no messages getting logged to Event Viewer that relate to USB, timeouts, disk events, etc.

Thanks in advance.

[Crunkimus]

I don't know necessarily what the problem is, but i have a guess. Maybe there is a program that runs when you turn on the drive that isn't normally on, and the program itself leads to a problem. Because if you totally shut down the drive and remove it, then the drive itself probably isn't a problem. I think you should set up a log that keeps track of processor and ram usage, and all processes which run. Then begin logging, and turn on the drive. Then remove the drive safely, and then try to shut down. Once you've done all that, start the computer back up and check the log. If you see a process start that usually isn't there, maybe you should check to see if it ends. I know i've had trouble shutting down when i've left a memory-intensive program running.

Other than that, no clue what's happening.
Good luck.

[Rampage]

Since it's a USB device, XP just recognizes it and talks to it on the fly - and other "mass storage" USB devices I plug in and remove don't exhibit this problem. However, I will certainly give that a shot and see if I can find something unexpected running.

[Rampage]

I think I found the root cause. I switched the hard drive from a USB 2.0 port to a 1.1 port, and the system shut down correctly. That USB 2 bus on my motherboard has always acted a little flaky, come to think of it (it would flat out lock up my system when I try to scan a document on it, but I thought the scanner was at fault), so I'll probably just pick up a USB 2.0 4-port card and hook it up.