I misunderstood and thought you had just started using Poser.  If you've been using it for years then this is not likely the problem.  Also, this works if your on XP--don't know about Vista or W7.  But if you want to try it anyway:

Right click on the desktop
Click Properties from the menu
Click the Settings tab
Click the Advanced button
Click the Troubleshoot tab
Bump the hardware acceleration slider down a notch. click OK and try to open Poser and see if it works.  If not, bump it down another notch, and so on.