Alright so first things first, uL (Urban Legends) has improved their ban system off the technique MTA uses by banning serials. Everytime you install GTA on you're hard drive a random serial ID is made. By banning that, makes you unable to connect to any of the main servers which you're serial is banned on. Reformatting you're hard drive removes the unique ID. Though they still log you're ip, use a proxy after reformatting and you should be good.
Be aware, uL also registrates names. So if you connect once with "Playername1" and then with "Playername2" it states on connect that you have the ALIAS "Playername1".