I'm getting the folowing error:
http://hastebin.com/kigupotovi.avrasm
What's wrong ?

Commited.

The query looks okay, i guess you somehow managed to create two bank-accounts with the same name.

I think someone changed his name and sombody else (with the same name) joined the server. So the 2 accounts are there.

#15 should fix the exception but there is still the possibility that you withdraw from the wrong account since Vault uses the username, not the UUID to find the account.