When I had the white-screen bug, it took 5+ tries to get in. After that, it behaved normally. This is when the server was hosted on one of my spare computers, and no one was trying to run a client and server on the same system. My step-brother has had it the first time he tried to log into a server that was running on his computer. It has yet to log in properly to that server, but logged in just fine when it the server was run on my spare.
There was a 3rd person playing with us who NEVER had any issues logging in to either server, but we suspect witchcraft!