If you are planning to upgrade to Snow Leopard (aka Mac OS X 10.6)

[Stiv]

http://forums.quark.com/t/21811.aspx
IMPORTANT UPDATE:
Quark recently discovered a serious issue when using PostScript Type 1 fonts with QuarkXPress, QuarkXPress Server and QuarkCopyDesk running under Mac OS X 10.6 Snow Leopard:
Text using a Type 1 font can shift position when opened on Mac OS X Snow Leopard, affecting the leading and vertical position of the text, as well as any drop shadows applied to the text. Quark is therefore recommending that customers who rely on Type 1 fonts not use QuarkXPress with Snow Leopard until this issue is resolved. Customers who don't use Type 1 fonts are not affected. This issue is specific to Mac OS X Snow Leopard only and does not impact other operating systems. Quark is working with Apple on a resolution. Please watch the Quark Web site for updates as we have them.