AccountNow Prepaid Visa Cards (Reload with Greendot, Moneygram, etc.). Yes this is an international card. It has worked for me more than 5 times now... never a kink or declined message... You can obtain an AccountNow card for free online. True, there is a $9.95 monthly fee for the card, but to me its worth it.
Also, I know it is not prepaid, but some banks* Credit and Debit have worked for me too. I have deposited using both options on Carbon Poker
, BlackChip Poker, and Hero Poker.
Hope this helps.
Edit: I have had NO SUCCESS with Vanilla Visa Giftcards, and other already loaded prepaid cards... Main reason being is that you HAVE TO HAVE your info on your Credit Card (Pre-Paid) and these cards always seemed to fail for me when it went to "Verify by Visa" page while trying to load money. No Success from those cards.