I have similar problem. Moving on to next round is always an adventure often ending up w/ 100% screen.
I used to just access consol (`) and type reconnect. This seems to solve most of the cases, but sometimes, it doesn't. It's odd; the map that freezes out is at random, and so is the server. I saw some messages, but there wasn't any one with "error"
i can't recall the exact last msg, but it said something about a certain thing being :0 msec. (redraw or memory something, i think?)
I tried connecting to other servers right after this problem (after reconnect failed) and i was in the game no problem. It's just that other servers have higher ping or have ff on, and being a noob, ff isn't my thing :p
I hope this helps to any degree... err... there isn't much detail
i wonder if it's some sort of port problem; i only allowed the corresponding UDP port open while having all TCP or other UDP ports closed to the application.
or maybe it's memory problem?