This is so annoying i just got it today and it is not letting me play league, it is saying that unknown DirectX error has occurred and League can not run. Pease make sure your video card is using the latest video drivers from the manufactures.
I'm having the exact same issue with the same error message, bumping for visibility.
Same
I've had the same problem occur as well, but only on the PBE. I tried a fix that worked for Windows, video below, to no effect.
Just got the issue as well on my Mac, live is fine but the PBE isn't working anymore
Update on the PBE side, the new patch seemed to fix it
