PM'd you weisan. You haven't found the lockup bug since the server will still crash and respond to you then...
Also, double check that the address being auto-banned isn't the one you're having trouble connecting from
Totally off topic, but just look at the timestamps on that logfile! Notice how the time increases between log entries by a minute and that given the times it appears that more than a few attempts from that address were suppressed to not flood the logfile? Gotta love that!
The AcceptEx() errors (121 = The semaphore timeout period has expired) means absolutely nothing to me except some internal problem (obviously not documented) with the winsock library again. BUT I have noticed similar issues in the past so keep an eye on the logfile to see if you always see such errors before things go wierd...
If you have 10 such AcceptEx() errors in the logfile between a server start and it not accepting new connections I know what's going on. So try counting them to see if it's 10, or perhaps just 4-5 but it's consistently 5 before it starts rejecting that's useful to know as well...