Oh thank goodness, I'm not the only one having this problem!
I, too, just bought Mesa of the Lost Women using PayPal. PayPal sent me a receipt and tells me the transaction is complete. But when I look at the "Orders" tab in "My Account" here at Rifftrax, the order is still listed as "Pending." This has never happened before. As with Darth Geek, my files have always immediately been available.