The site returned a bunch of errors I didn't capture, because when I re-tried it just started claiming "Invalid File". They looked like some kind of internal parsing error, and they all started with "vb_".

I'll post a copy, if I can get those errors to show up again.

I've cleared my cookies and cache, restarted the browser, and tried a different browser.

I also copied and renamed an image file on my computer that I have successfully uploaded before. It now fails to upload too.