I am running windows 7, I found a work-around kind of fix for it that worked for me, in another thread a Riot employee told someone with the same problem we're having that their lolclient had been changed based on his log, so I thought it might be my problem too, the answer being to get a new, clean LolClient. If you try this make absolutely sure you copy the old one or just move it somewhere else in case you have to undo it, but what I did was moved it to a temp folder on my desktop, downloaded the stand-alone patch for the 4/27/10 patch and just copied the LolClient from the standalone patch to where the old one used to be (in the air folder). This actually fixed the problem for me, use at your own risk
LOL@post above mine, if figured it out but thanks, glad to know i was thinking the right thing 