OK, so this is what I've done to get the fonts to work...
Restarted Mac in Safe mode (hold down shift while re-booting)
Then restarted again in regular mode - this resets all the caches - not sure if this was necessary but it's always good to have a clear-out!
But I think what really fixed it was to remove all my fonts from the MacHD/Library/Fonts/ and MacHD/Users/me/Library/Fonts folders and dump them all in a temporary folder - essentially uninstalling all my fonts.
I then installed the hitherto troublesome fonts and they worked perfectly in Flash - without restarting and without clearing the cache using Font Nuke.
What can I conclude:
Flash and Fireworks use separate font caches.
Flash seems able to deal with less fonts than Fireworks
Adobe have been bloody lazy at testing their products
Why don't they use the Mac caches, surely that's why they are there?
In all I've wasted 5.5 hours on installing three fonts - aargh - leaving me 3 hours to do a days work - aargh
Anyway, I hope my posting is of use to someone else out there.
I'm sharing my solution as well so that it might help others out there who are desperate for a solution to fonts not showing up in Flash CS4 (and other versions) on OSX. I've spent so much time reading various message board posts and blog posts about this topic. There seems to be a lot of confusion and misinformation out there. Hopefully this can help someone out.
In my situation, I had been using FontBook for years to install and "manage" my fonts. This meant that all my installed fonts were stored in User/UserName/Library/Fonts . Like most designers, I was managing thousands of fonts. I noticed that a lot of fonts weren't loading in Flash CS3 and later CS4. My solution at the time was to minimize the amount of fonts that I had active (I tried to keep it around ~500) and then do a Font Nuke and pray that they showed up in Flash. I'm sure if you're reading this thread that you can relate to all of the frustrations of getting something so trivial to work in Flash when it works in all other CS applications. This solution worked sporadically at best. This was beginning to affect my design work, because I knew that if I couldn't get a certain font family to load in Flash (despite endless nuking and font installing/reinstalling), that I should avoid using it in my proposed designs. This is a horrible feeling so I sought out a better way.
Eventually I made the move to LinoType Font Explorer X (it's free too) to better manage my font library but the problems persisted. From Font Explorer X I could easily clear the System Font cache and the Adobe Caches but fonts didn't always show up as intended. I then noticed that even though I was using Font Explorer X, all my fonts were still residing in User/UserName/Library/Fonts. I decided to move them all out of there and pretty much start from scratch. I moved them all to another folder on my desktop and readded them to the Font Explorer X library and then activated ONLY what I needed. I found that this was the first time that everything worked as I had intended. Even though I had been nuking and using Font Explorer to clear all the caches, the fact that those thousands of fonts were still living in that Library/Fonts folder was messing it all up. Now that folder is empty and things are working properly.
My advice: Avoid FontBook and use LinoType Font Explorer X to manage all of your fonts. Remove everything from User/UserName/Library/Fonts and place it into another folder. Import everything to the Font Explorer library and activate only what's needed.
I had the same problem but none of the solutions above worked for me. After nearly going crazy i found a workaround that does the trick for me.
I noticed that Flash displays all the Mac system fonts. These fonts are not in your user library (such as MacHD/Users/You/Library/Fonts) but in your computer library that you can find in the root directoy of your mac os x hard drive (so usually that would be Macintosh HD/Library/Fonts).
So if you move the font that you need in Flash from your User Library to your Computer Library the font suddenly shows up in Flash.
As you can read in the posts above you cannot effectively use fontbook when using flash, which is really a major pain in the ***.
Therefore my way of organizing fonts is now to have the basic fonts in the computer library and all the other fonts in the user library. If a needed font doesnt show up in flash i move it from users to the computer library.
I hope this helps.