Admin Panel thinks I forgot to choose an image to upload

[ally]

Me and my co-admin have both tried uploading images today.

All of the sudden the "add images" feature isn't working. After submitting the upload, it reloads with the red notification "Image *" that basically says I didn't choose an image to upload, when I most certainly did. It does the same thing with uploading from a URL, and it's not just the one file, I tried many.

I certainly haven't changed any of the script files since upgrading a long time ago (1.7.6).

Please help, I don't know where to begin with this!!