Okay, I figured it out. Vometia's suggestion worked - I did it before the other suggestions and it seemed to work. Thanks for the suggestions though, I'll use them later if I need them.

The 4GB Launcher puts a TESV-4GB.esp file in your Skyrim directory. Delete that.

It was actually NONE of the above... at least for me. The problem was, for whatever reason, the Skyrim executable was marked to have Administrator privileges after the re-install. I don't know if it was like that the very first time I installed the game, or only after the patches (I'll assume the later).

In another thread Nepentheia suggested this might be the problem... that we should UN-check the Administrator privileges for the executable. And I'll be! It worked. The game is up and running again. YAY!