Ok, I tried the repair utility in Origin. Admittedly I should have thought to do this right away, and I'm going to look like an idiot if this fixes the problem.
But at some point after starting the repair it's trying to install something that's 8.89mb. It's wavering back and forth between 30 and 31% done, shows no signs of increasing and no download speed, and it decided to start unpacking all 34gb of audio again.
If I wasn't so sleep deprived and annoyed I'd probably find this mysterious misadventure hilarious.
I don't even know what that is, so I'm assuming no.