The game launches properly, can be heard starting. But the screen stays completely black, no visuals at all.
Temporary fix: obviously a real fix needs to be found, but you can change your windows resolution to 1024x768 (or whatever's lowest) before you launch the game every time if desperate.
Fix: Run game as administrator.
%USERPROFILE%\Documents\My Mods\SpecialK\Profiles\Rayman Legends.exe\SpecialK.ini