mp4 insertion breaks module

I am working on a module that had only text so far. I inserted an mp4. The mp4 plays fine in preview, but when I publish, I get the spinning wheel.

Now, the module is completely broken. I deleted the mp4, removed the whole slide, and when I publish, I get only the spinning wheel.

So, to test if the mp4 is the issue, I made a brand new module, one slide, and inserted the mp4, published it and it plays fine. 

Does anyone have an idea what might be going on here? I have tried this on two different computers. I am working locally. This video was an flv that I converted into an mp4 in another program.

Thank you