Had to go speak to my bank, turns out that Gumroad came up as fraud and HSBC froze my entire account! The bank said it should work now but I'm pretty put off.
I had exactly the same issue with my Royal Bank of Scotland account - Gumroad was flagged as fraud (the security people at RBS said they had several complaints about Gumroad) and I had to get my account unlocked.
People using British accounts - be VERY wary about making payments to Gumroad. I'm waiting till this is available on PayPal or Amazon.