Okay this has been fixed now. I can now see the fonts correctly in the 32-bit and 64-bit versions of Firefox 4. An oddity though is under the suggestion of Claus I did run Firefox 4 32-bit in safe mode and the page rendered fine. Now safe mode is suppose to disable all add-ons as well as bypass any custom configuration settings via userChrome.css and userContent.css (not that there were any on this particular profile) and the page loaded fine. So thinking it was a bad extension or plug-in, I started disabling them 1-by-1. With all the extensions and plug-ins disabled still would not render right. More on this later.

Back over in the Firefox Builds forum I was informed that 64-Bit version of Firefox will not be officially supported until Firefox 5. However, they believed the issue was being caused by the Windows Font Cache. They provided these directions:

1. Type “services.msc” into the Start Search bar and hit Enter.

2. Find the Windows Font Cache Service, select it and hit “Stop”.

3. Open Windows Explorer and navigate to “C:\Windows\ServiceProfiles\LocalService\AppData\Local” requires admin privileges

4. Delete the FontCache dat files. (They will be regenerated over time.)

5. Restart the Windows Font Cache Service.

6. Using Bluefang’s instructions, Create a new Firefox profile.

Except I skipped step 6 and started Firefox 4 RC1 (32-bit) profile (which had no extensions or plugins active) and the page loaded fine. Fired up Firefox 4 Beta 13pre (64-bit) and also worked fine.

So back to safe mode oddity. It was explained in the Firefox Builds forum:

Safe Mode disables Hardware Acceleration.

Firefox 4 on Windows 7 & Vista uses Direct2D and DirectWrite for Hardware Acceleration. DirectWrite uses a font cache to speed up operations. The cache was probably incomplete due to the enumeration bug that Microsoft patched a couple of weeks ago.