This has happened at least 3 times already. With each patch, my client gets screwed up and I can't use it. It goes through a loop of screens but never successfully patches. This is what happens:
1. I click the desktop shortcut and it loads the client.
2. A screen pops up saying "We have restored this installation to an older version of League of Legends. Now we'll try to patch it up to the latest version." Then I press the Okay button.
3. "Patching failed and we're not sure why. Please restart the client to try patching again. (Error code 004)" and another okay button appears,
4. It automatically starts trying to patch but says "There was a problem patching League of Legends. We'll restore a backup version and try patching again after you restart the client" or something along those lines (it automatically goes to the next screen)
5. It says "League of Legends needs to install a required update. This will happen in 3..2..1.."
6. The League Client loading screen appears with an ETA of 0 minutes that never loads.
7. It goes back to the countdown screen, then goes to the ETA screen, and loops.
Uninstalling the alpha and reinstalling fixes it until the next patch.
Something else I noticed: In the Desktop files under "this PC", the old League client shortcut is there, but the new alpha is missing.