Uninstall Pando Media Booster. It installs when you install the LoL client. You don't lose any functionality and it seems to have broken the LoL client in the recent patch.
The other recommendation was disabling the IP Helper service. Not 100% sure on the downsides of this one but you can always re-enable it if it causes problems.
Thanks for the heads up, will uninstal pando when i get home (just read what it is and thats ridiculous).
Also what is IP helper?
Cheers.