Follow-up for others who may have the same issue:
I can't get the Sprint insurance. Have to add it within 30 days (I think) of buying the device, and I bought it over a year ago on eBay.
I'm sure it's not a PC issues, as I'm not up to 8 different PCs (XP, Vista, and 7) and none of them recognize it, but they all charge it. Weird...
Just bought another one on eBay, so I may play with flashing it via a Bluetooth-transferred ROM. Then again, I'm sure someone could use the unscratched glass or other components of it on eBay...maybe.