This is a bizarre one. My IB with Sierra connection has been running fine for years. Today when I log onto IB and click yes to connection attempt, the TWS just freezes up and I need to use task manager to shut it down. Haven't used the trading machine since I switched it off Friday, only thing I did do was install some XP updates. Thinking this was the problem I uninstalled these updates but didn't help. Now here's where it gets bizarre. If I log onto my paper trading a/c, it will accept the Sierra connection. It just doesn't like my production a/c for some reason. I tried uninstalling and re-installing both Java and the TWS but made no difference. Anyone experience this before or have any suggestions?