I find your post a little confusing because you don't say if you were ever able to create PostScript from Quark or if this problem suddenly just popped up after weeks/months/years of working properly. So...
If it's never worked before then you may need to setup a virtual PostScript printer (instructions towards the bottom of this post
). Or you could just try printing to the Adobe PDF printer.
If it used to work and now suddenly doesn't you may need to trash your Quark prefs.
Let us know how you get on. And don't forget you can also Search
the forums for more help.