When I set up a server connection with my registered nickname (_0x783czar) I get the following error
*** Your username is invalid. Please make sure that your username contains only alphanumeric characters.
Closing Link: 220.127.116.11 (Invalid username [~_0x783cza])
there appears to be an issue with how my username is being parsed by the program.
If I set my username to something else, and then change it back with the /nick command on the server, it works just fine.