When I run the repair tool I get:
An unknown error (2231) has occurred when attempting to download data.
I have yet to try reinstalling, as it takes hours to download, but if there's no other easier suggestions, I may just have to try.
I'm running the Vanilla game on a standard edition account. I can post system specs if needed, but it was running just fine last week.
EDIT: The launcher will no longer get past the Initializing stage.
EDIT 2: I tried launching via SC2Switcher.exe and had the same thing happen, but this time when it quit to the launcher, it went past Initializing and started updating. I guess if this happens to you, try that.
EDIT 3: May have been my firewall changing my settings. I feel slightly like a bit of a moron now.