[LAUNCHER] Can't launch League!

Ever since patch 4.21, I have not been able to launch league. Patcher opens fine... but when I click "Launch," the patcher disappears as intended but the client never loads up.

LoLPatcher.exe, LoLLauncher.exe, rads_user_kernel.exe, and LoLClient.exe all sit in task manager until I manually end the processes.

My PC: Windows 7 64-bit AMD FX 6300 4.6 GHz OC AMD Radeon HD 7800