Did you include the notes to the buyer inside the Paypal refund? I've found people usually miss that one. You could try sending a seperate email, send it through Ebay messages so buyer will get it in ebay and in ISP. That's what I've done in the past...You would think they'd wonder tho, why they keep getting refunded??

I really hope it doesn't go to non-reciept but if the buyer is as oblivious as s/he sounds, s/he probably isn't even aware of that option.