Looks like another fellow is having the same issue. I've tested it but haven't been able to reproduce it. Would you be able to follow the steps in the following post, and then post your results in that topic so that we can keep the info together?

http://www.displayfusion.com/Discussions/View/start-menu-on-2nd-screen-malfunctions-in-xp/?ID=2edda248-2e09-4fe2-8b38-4c59e6a874ae#b3867b40-58d2-400b-ab8f-00bb7cf1f5af

Thanks!