I cannot see most of the fonts in Illustrator CS5, I just installed Yosemite OS last night and this morning the font menu isn't working.
I had the same problem. Here's the solution I found after searching around a bit:
Open the Mac OS X System Preferences and head to ‘Accessibility.’ Once you are in there, select ‘Display’ from the left-hand list and then check the checkbox that says “Reduce transparency.”
After doing that you should be able to see the font list properly again. I don't know why it works, but it does!