Doomed to calculate differences... For Eternity.

Launched the LoLClient (mac user) for an evening game about an hour ago, and have since then encountered the dreaded "Calculating Differences | ∞ files scanned" problem. I remember having this issue somewhere in the mid-late 4.x Patches, and can't remember what I did. I can only think to reinstall the client, but I have found evidence that that doesn't work for some, and dear god I don't want to wait 3 hours for it to reinstall just to have the same thing happen again.

Please help.

EDIT: Third client relaunch, 5600 files and counting. High Score?