If you have rcon access, try this:
rcon_password "enterhere"
enter key
rcon ulx removegroup "superadmin"; rcon ulx addgroup "superadmin" "admin"; rcon ulx adduser "yourname" "superadmin"
enter key
If that doesn't work, then the best bet is to re install ulx/ulib and deleting the currently existing data/ulib and data/ulx directories
Don't quote me on this. Simply what I would do