You got the SVN from github, not ulyssesmod.net, right?
If you got the latest from our new repo (github);
It REALLY sounds like something on your server is conflicting with ULX/ULib.
Never in my years here have I seen anything prevent players from joining within ULX itself (bans aside!)
It's a pain to do, but did you try removing all other addons but ULX and ULib?
(including a game mode)
Tried a diff gamemode?