unknown direct X error. have re-installed, still cant load

Bit of a weird one. I had the 'discord overlay' bug which I just found out about today, but wasn't aware of it when i was playing. I quit the game with task manager, relaunched, same thing, so i rebooted my PC.

Then, when I tried to reconnect, it comes up with 'unknown direct X error, cannot launch, ensure drivers are up to date' etc. I check my drivers, they're the most recent. I uninstalled league, re-installed and re-downloaded the patch, still no dice?