Same problem - AGAIN.
I'd like to use these guys more but every time I give them a shot they just screw up my arbitrage.
The thing is, the reason this keeps happening every time you use BitInstant for arbitrage is because the arbitrage opportunities wouldn't have existed if BitInstant were fully operational. Thus, when you see such unlikely opportunities, only send as much as you can go without for a few hours, and never execute a trade on the side that already has funds until the other side has those funds.
+1...I've only been moving sample amounts. I don't throw a whole bunch of money at anything right away, and I advise others to do the same. Bitinstant is still new so I understand they're going to have growing pains.