Hey ThePhail. I think that you should definitely test the drive so that you know what's going on with it. You can do it with DLG (Data Lifeguard Diagnostic software). I'd recommend that you run both tests (regardless of the time they take to complete) - Quick and Extended and see what's happening exactly.
You could also try the drive with another computer to see if you'll have the same problem. If the drive is indeed failing, you should do your best to backup your important data or at least stop using the drive until you are able to get an external one for backup or figure out something else. Because when a drive starts to act up and it starts to fail it could be days or weeks or months before it completely gives up, but you never know exactly how long it's gonna be. Also does the drive make any kind of unusual sounds/noises when it spins?
You can download DLG from here:
http://support.wdc.com/product/download.asp?groupid=810
Good luck with your drive. Let me know what the tests show.
Boogieman_WD