They (and I can't mention the company I bought from) are allowing me an even swap for the hard drive. If by some strange event the error continues with the new drive, I'll repost here.
The hard drive was a 1TB WD Caviar Black, similar to the 640gig I already have but larger.
I'm wondering if it is the way these HDs are being shipped that is causing much of the problem. Throwing the drive into a box with a few peanuts isn't real secure and really makes the thing bounce around inside.