External USB HD can't be removed safely

Hi,

I just bought a WD Passport 320gb external USB hard drive. It works fine
EXCEPT, I can try to safely remove and it tells me the drive is still in
use. There's no explorer processes running...I can safely remove my microSD
cards just fine. I already checked to make sure system restore was disabled
for that drive. Indexing is also disabled. But regardless of what I do,
Vista insists that drive is in use when it's not.

I really don't wanna pull the plug or reboot EVERY TIME I want to remove
this because i'd spend more time waiting for this trainwreck to boot up and
shut down.

XP does not have this behavior.