I'm having the same problem.
Font files are OpenType, all from same family called FU24 (different styles of the same family - e.g Bold, Black, Bold Condensed etc.).
All fonts were tested and worked on Windows XP machines.
After installing the whole set of fonts (23 in my case), only 2 appeared on the 'windows fonts control panel' / 'windows fonts library' applet.
When uninstalling these 2 fonts, they disappear, and then one or two fonts that were previously hidden are now magically shown!
In addition, if I install the fonts individually (one by one), first one appears, and when I install a second font from the family it will either show, or not show, depending on some kind of logic windows incorporates by which some fonts are actually the same, in which case it automatically disables all contact the user may have with these files.
The fonts also don't show on any of the installed software, including Microsoft Word and Notepad.
Guessing, I'd say the font managing process somehow recognizes some fonts as identical, though they are not, thus disabling all "copies" of the same font.
This makes work with fonts in windows 7 practically impossible.
Please solve this.
This is not a user specific problem, Chris H. It's a problem with windows's fonts manager and the problem should be addressed as such.