Well, it took a week and several emails and one PayPal complaint later, but I finally got a refund from Buy.com. In the interim, I ended up buying a nice 32" LCD HDTV from Costco. It's great!
Also, all the other stuff I needed (wall mount, HDMI DVD player, cables) I ended up ordering from various places online that take PayPal, and guess what...the payments made it through no problem!
So I will never use Buy.com with PayPal again. They seem to have an issue with their PayPal integration and will cancel your order in 3 hours if they don't think they have the money. Sons of bitches.