Cannot submit model (getting error)

I just created a section for a new game on tMR (which correctly shows up as pending). My problem is that when I try to submit an NPC model I ripped, it does not accept my upload, and it tells me "Error: Model must be a zip archive.". I've tried compressing my models with both WinRAR archiver, and Windows' built in compress folder function, both producing vaild .ZIP folders. No matter which I try though, the uploader still will not accept my model. Is the site not working correctly, or am I doing something wrong?

EDIT: Nevermind, it appears to work fine when submitting with Chrome instead of Firefox.