In 2007 Pantone updated their CMYK color builds for PMS colors to create better CMYK matches. Many of the common design programs are using the  old cmyk color builds. Quark 7 and Quark 8 both come with the current CMYK libraries. If you are using Adobe CS3 or earlier you will need to update your libraries. To ensure the best CMYK color match of your PMS color you should visit the Pantone website and go to the support section to download the updates.
www.pantone.com