Client fails to launch

The LoL client will not actually launch after I click launch on the patcher. Played for an hour or so yesterday so I know it worked recently. Tried launching as administrator and restarting my computer to no avail. Lastly I tried to repair it but that seemed to do nothing as well.

• Started up league today. I keep League on my taskbar usually, but have since tried the desktop icon. After I click launch, the mouse spins for maybe 5-10 seconds, then nothing.
• Trying to open it again gives me the "An instance of this program is already running" error
• went into task manager and found LoLclient.exe, LoLLauncher.exe, and LoLpatcher.exe all still running.
• Closing those gets rid of the Windows error and brings up the patcher again, but its the same story.

What's going on? How can I fix it?

EDIT: I should also mention I'm on windows 7