My experience with Lua doesn't give me much input as to how to fix it.
However, more and more people are growing aggrivated with the fact ULX often fails on map change until a player reconnects.
Look in our posts here.
Look in our ULX release thread at Facepunch.
http://forums.facepunchstudios.com/showpost.php?p=10457595&postcount=1814In that particular discussion, he links to another forum in which several have gone to other mods.
Megiddo, I know you keep mentioning it's on our(your) 'to look into' list.
I strongly recommend putting it at the top, if not already there.
Even if the issue isn't truly ULX, but the way Garry works with usermessages on map change/restart, it still needs to be fixed/work around found.