Had this problem tonight. Tried several times to load and reload, but no luck.
Then I looked down at my taskbar at my antivirus (just switched to Webroot) and there was a little lock icon over my Webroot icon. When I moused over it, it said "The foreground window is protected by Identity Shield". I clicked it, the lock went away, LoL immediately opened the PVP.net Patcher and started working normally.
Not saying this will work for everyone, but if you're still having this problem it might be worth a shot to check out your antivirus.