While playing an ARAM I was unable to cast Lux's E after a certain point. Unfortunately I do not know exactly what produced the bug, but my hunch is an interaction with silences.
After it became unusable, I noticed the mana cost had reduced to 0 as seen in the picture. Perhaps this is what caused me to not be able to cast it?
Just happened to me and I commented in the other thread. Almost cost me a ranked match.
Match in question: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1944956368/42941535?tab=overview
I couldn't cast E for the last 20 minutes or so and I have no idea why. I tried dying on purpose. I tried restarting the game from login screen. Nothing worked. I was playing with one hand tied behind my back.
http://www.veoh.com/watch/v94135451KK2FDmx8
Same thing happened to me during a normal rift game. I cast it and it didn't work, then was grayed out for the entire match, even after multiple re-logins of both the game and the client. Nothing worked (even tried dying) to get it fixed, so I decided to make a short video.
Happened to me too, I made a thread right before I saw your thread.
http://boards.na.leagueoflegends.com/en/c/bug-report/lQwmu7i8-luxs-e-cannot-be-casted-the-whole-game
