If there are fonts installed that do not work in Firefox then your only option is to move them temporarily out of the Fonts folder while running Firefox if you do not want to remove them completely.

@cor-el I have the exact same issue! And am going mad trying to fix it. I am also a GD and have nearly 2000 font, and dozens of Helvetica options…

I was using Firefox as Safari was really buggy and kept crashing… but I suppose that's better than this Font nightmare!

On Mac you can do a check for corrupted fonts and other font issues:

• http://www.creativetechs.com/iq/garbled_fonts_troubleshooting_guide.html - CreativeTechs Tips: Garbled Fonts Troubleshooting Guide
• http://www.thexlab.com/faqs/multipleappsquit.html - Font Book 2.0 Help: Checking for damaged fonts

I have had this issue too. The problem for me seems to be Helvetica Neue. I actually had 2 versions of the same group of Helvetica Neue Variations installed, I uninstalled most of them (for some reason 3 variants just wont uninstall) and the problem appears to have gone.

In Windows 7, in the Font folder I selected the Helvetica Neue bold fonts and then selected 'Hidden' for that fonts (not deleted them). Then the fonts didn't show up again. I will report if they show up after a few hours/days.