This has been reported a number of times before. The cause traces back to a problem font or font suitcase--often a duplicate. I'm not a mac users so can't give you the step by step, but removing the problem suitcase fixed the problem. You might glean a few more details if you search the forum for "Snow Leopard Font" or Just "Snow Leopard". Snow Leopard was the first OS upgrade to produce this issue.
I have the same "dispersion" of MacOS/Windows and FMP variations. All Mac/FMP programmers should now be aware of the fast pace "changes" in AppleOS and devices. Fonts should be "Web Friendly" thus Windows, MacOS and Display resolutions are fully covered. Check Apple support for "web friendly" fonts.