I'm posting this, because i know how frustrating those errors are. It took me about 3-4 weeks before i got my game running again, the problem started after the server split.
So here are the list of things that i did:
1) Disabled firewalls, one under the control panel and the second under the antivirus program preferences or (options) I have Bitdefender 2011.
2) I had deleted the temp file in the Riot Games main directory.
3) Running the game as admin.
4) After the server split, uninstalled the game (about 10 times :S ), and downloaded again under my region.
Though every time i enter the game i must disable both firewalls and not the Hamachi adapter (if you have Hamachi).
I hope this helped in any way, tried my best!
Btw, i'm on 64-bit Windows 7.