As far as I know a valid credit card should pass validation regardless of the type of card. This is at least the way that it works here in the US. It is possible that there could be some other checks that are occurring for the card, like a geographic restriction based on where the card was issued. You should definitely get in touch with PayPal to get a more specific reason for the checkcard being rejected on the cvv value. If you find out any additional info on this please post back here with it so others can benefit from the knowledge.