Most perpaid VISA cards won't work...if you do find one DON'T post which one works in these forums. If someone already knows, PM OP don't post in these forums.
OP, just use Western Union to deposit, it's a lot easier than searching out which pre paid cards work and which don't. Back in 2004-2006 most pre paid cards worked. The issuing banks of these cards have caught on for the most part, and these days the vast majority of cards won't work.
Try depositing via the casino if you have a credit card that is being declined. The casino has a MUCH higher success rate with US credit cards, they even accept my debit master card!
Other than that, western union would be your best bet. Idk about the pre-paid's anymore. I have heard that they usually decline your first and second try, but if you keep trying, supposedly they eventually go through. That's what I have heard atleast.