This was zion's answer to the same question i asked a few days ago.
Zion Fox wrote:
The problem is a current recurring bug which i am not 100% sure on what causes it, but i'm 99% sure it's memory and sockets based.
What happens is, throughout the day (especially over the last few days) many people connect and disconnect from the server, and when the server is full, people try to connect and are disconnected immediatly. From here, my theory is that the sockets remain open, which take a small amount of memory, however many of these open sockets will take a large amount of memory. At some point which i have not yet defined, the server refuses any more connections, which displays the end user an infinite connecting screen. The people who are still playing will remain connected until they go, or the server restarts.
When this happenes, best way to resolve it is by contacting either myself or chris when we're online (IM or steam is best). We'll restart the server, which 'resets' everything.
Hope this helps.