I sat in front of TWS for >45 minutes after trading opened on Sunday, watching my very marketable order to close a position unable to execute. Initially I had a limit order to buy which was about 12 pips *above* the market, and it would not execute. I tried putting in a market order, but that didn't help. I watched for the next 45 minutes as the market traded up to and through my limit price, still no execution. Finally, for some obscure reason, the trade executed at my limit price when the quoted ask was 2-3 pips below my limit price. I'm also trying to close a position in another pair. For the last 30 minutes the market has been below my bid, and it still won't execute. IB tech support is unable on Sunday until 6:30, so no help there. As I watch at this moment, the orders, for some unknown reason, are finally executing. Very frustrating, and very expensive.