11/06 NDX Iron Butterfly - Paper

I did a vertical roll on my NDX Iron Butterfly, didn't quite move all 5 spreads, only 4. Then I sold the long DEC CALLS I had. One thing happened when I was selling those calls: One of the sell orders wouldn't get accepted, it said I didn't have enough marging to sell the contract. I'll have to double-check with TOS to find out why, since it was a contract I already own, I should be able to sell it without changing my margin requirements. Live and learn here...