I have also tried unsuccesfully to get MathML to display right in Firefox. I am using ubuntu but my guess is the problems are the same.
The most promising pointer I found was the following:
http://rooster.stanford.edu/~ben/notes/
However even after following these instructions, MathML didn't display right. I was not really all that motiviated so I might have done something wrong and then given up too easy.
If you do get this figured out, I hope you will post the solution that you converge on.
- Dave