Not sure why you got that error, unless it was because a gmod update causes that error since the 'release' version your using is old.
May also be because the Windows 'user' that the game is running as doesn't have write/modify access to the gmod subfolders.
(Not sure how Windows 7/Vista work now in regards to that)
Debug looks normal, but you weren't connected.
Ok, this next step really has nothing to do with ULX, (but ULib will import from it), add yourself to Gmod's users.txt file so ULib knows you will be superadmin, AND, all other mods that require superadmin access will know.
http://wiki.garrysmod.com/?title=Player_GroupsShutdown serve, add yourself.
Though that example uses player in both super and admin, don't place yourself in both, and, don't use // in front of your username (just like that article says)
Just put yourself in the file garrysmod/settings/users.txt as superadmin with no //
If after you start server up and still ULX still won't allow you superadmin commands or status, though Gmod does (Gmod will give you a 'welcome RT, you're a superadmin on this server' in the chat window when you join.
Bring back another debuginfo file while you are connected to server, run it from server console.
You can attach or paste in your /settings/users.txt file too so we can verify you've added yourself.