Motion 1712 Error after adding fonts

I can't figure out why for the first time, Motion suddenly won't open on my mac. I'm guessing it's because I added some old fonts to my computer yesterday because a printer had asked for them for a project they were working on and the CD with the fonts could only play on my computer.

Today Motion won't open at all. I know Motion has a lot of fonts, and I'm hoping I didn't mess it up by adding fonts to my computer.

Is there any way to check on what the problem is? If I reinstall Motion---which would be a terrible process---will I lose files already saved as Motion files on my computer?

Please help! Thank you

-David