steven r,
at first I thought your problem had to do with a really large family tree.
But, if this is happening with a 3 or 4 person tree, I would like to know a little more about your PC to understand why this is happening.
What version of Windows are you using? Have you installed all the recent Microsoft updates?
What processor do you have?
How much memory do you have?
Are your video drivers up to date? What video board do you have?
How big is your hard drive and how much free space do you have?
Do you see similar problems in other programs?
What version of Internet Explorer is installed on your PC? (Family Tree Maker is closely tied to IE)