Larian Studios Forums Divinity - Original Sin Divinity Original Sin - Mods [BugReport] Editor - Reappearing Message

Check this guide:
http://steamcommunity.com/sharedfiles/filedetails/?id=276611375

"WARNING:
Opening the editor and Main story mod will spoil the game! Do not open the editor/Main mod if you would like to finish the game without spoilers! Do not save when the main mod is opened. This can break the game and data/levels!"

No need to re-install the game. Just delete the folder ...\Divinity - Original Sin\Data\Mods...

You need to 'Mod' the main campaign, not alter it directly. At the moment when you create a new mod and select Main as dependency it show no levels, this will be fixed today.