I had a problem when placing a bracket order with a stop limit entry awhile back. Since you couldn't attach a bracket to a stop limit I'd create a new limit order, hit bracket, and then change the order to stop limit.
Come to find out the bracket orders were only good for the day, although they were marked GTC and were there in the system. Some bug IB fessed up to after a few e-mails. I had a couple of positions run stops (ironically, I watched them closely when I caught it and worked them back to get out).
I still go in at the end of the day and create new OCA orders for fills during that day just to be safe. I think IB fixed the problem, but I haven't had the time to test it out.
It was funny, though, the brackets worked perfectly if the target or stop were hit that FIRST day. It took me a couple of days to see the problem arise.
I love the bracket and OCA order features in IB. Just good to keep an eye on things early on.