LE: I got it!
First, I tried the debranding + Zune... but nothing (LG Quantum AT&T, but I live in Romania).
So, I've used the SevenEighter app and that worked superb. The app will crash after each successive update, and you have to reselect the languages (6 for me) existing on the phone before each install. But other than that, works just fine Got like 4-5 updates (I think from 7720) till 7.8.