I've had this happen on two separate computers so I'm pretty sure that something may have changed, but when I attempt to use Ninja Trader with the latest version of TWS (build 854), Ninja Trader won't connect and IB goes through some sort of login loop. If I use the new version of TWS by itself, it immediately connects with no problems. I've manually rolled back to an earlier version of TWS and everything is now working again. Has anyone else experienced this, and if so, any known workarounds? Thanks. ~Alan