I have a similar problem to the thread of "Usermin connection error", in that I can't log in. (I'm using Virtialmin Pro and it seems to of started after the 3.63 updates. At least that is when it was brought to my attention). I however can get to the login page. What happens after that is that after entering the username and password in, it just reload the login page. But I know that there is nothing wrong with Usermin because if I load the page with localhost:20000 it works. Also if turn off the firewall to test it does the same thing. But what I think is wrong is Usermin isn't allowing from the outside. I've checked the settings and have no restrictions set. When doing:
lsof -i :20000 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME miniserv. 914 root 5u IPv4 137633133 TCP *:dnp (LISTEN)
lsof -i :10000 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME perl 26110 root 5u IPv4 127819402 TCP *:ndmp (LISTEN) perl 26110 root 6u IPv4 127819403 UDP *:ndmp
So I think the diffence between first and second settings is the problem, but I don't know how to fix it.