There's no going back from UP3.0 RC4, unfortunately!
You should keep a "vanilla" 4.10.1 installation with nothing else. Then, when a modpack stops working or you want to install a new one, you copy the 4.10.1 installation and install on top of that.
Right now I would reinstall from scratch... delete the game, then install it, use the "megapatch" to get it to 4.10.1, then copy over, and then install UP3.0 RC, then UP3.0RC2, then UP3.0RC3, then UP3.0RC4, just like in GunRunner's instructions.
Good luck!
