Plenty of reasons to ask questions on this one , artx .
Did this buyer actually place a bid on the EBay page for your item , or was it via an email contact only ?
You could always suggest that the prospective buyer should contact Paypal , so as to straighten out any problems they're having with the service (in the event this buyer is legit) , esp since "it's not your problem" artx , IMO ... for starters .
I betcha others here will have good/better suggestions too !