In the case of OpenType fonts and QuarkXPress, the word out on the street is that regular version of QuarkXPress deliberately suppresses all "foreign" fonts from working.
If you want to use these types of fonts and have access to the extended character sets and features that they offer, you'll have to fork over more money for the QuarkXPress Passport version of the app.
Funny, 'cause I could build a text editor like TextEdit with full Unicode support in under 10 minutes, and all without a single line of code.
Dual 2.7GHz PowerPC G5 w/ 4.5 GB RAM; 17" MacBook Pro w/ 2 GB RAM