I'd suggest clearing the font caches. You can do this with Linotype Font Explorer (a much better, in my opionion, font management utility and it's free) or something like Onyx.
I've had problems with Optima and a few other fonts in the past - purely Quark related too. That was back at my last company using v6.52 on OS 10.4.11. We had to clear the font caches everytime we needed to use Optima and one other font I can't remember the name of right now! After clearing them all worked fine for a while, then we'd have to do it again. Irritating, but it worked.