Unfortunately I think you may be out of luck. The issue is that your new limit of 0 prevents you from paying the fee but a transaction fee is required to prevent the network from being spammed. I also believe that setlimit tx's can only have 1 input and 1 output so that it can be detected as a setlimit transaction. So basically I don't think there's any way it can be undone. Originally we were going to make a withdrawal limit of 0 signify an unlimited withdrawal limit but it made much more sense to do it the way we do it now. We probably shouldn't have allowed the limit to be set to 0, but it could be useful in certain situations where coins need to be destroyed without having to send them back to the coinbase account.