Remove ALL addons/subscriptions, put only Ulib and ULX back on, test and see what happens.
Two possibilities, the second more likely - first, bans became corrupt, ULib attempts to check its own bans file, rebuild it.
Permanent bans are not usually touched in this instance. (ULX uses the standard gmod bans file for permanent bans)
Second, sounds like an exploit - remove all recently added addons/subscriptions - if youve not added any lately, one of them has been updated to include exploit.