Hey there! Styrka here.
So, this has happened to me twice now: I'm in an arena and my hot keys just turn off! Only ever in arenas though.
What I mean by that though is that 'w' no longer moves me up, nor can I type anything into chat boxes. I checked, and it's not a problem with my keyboard, because I can type this just fine. Rather, I have to go and put new values into my keys in hopes that they will stay. Sometimes the values stick, others I revive only to be swatted down again, unable to do anything.
Any ideas?
-Styrka
Last time I had something like this happen I removed the Java properties for "projectx" and it fixed itself up after. You'll need to change all your options and hotkeys back after though.