The issue is related the amount of programs running in the background. Windows Mobile uses a feature called Smart Minimize, this leaves programs running in the background after you X out of them. Some applications have an exit option which allows you to close the application entirely (in KForce see Tools->Exit), but most do not so when they are closed they are still active in the background.

To clear the applications out of memory, click on Start then Settings. Click on System then Memory. Click on Running Programs. A list of applications will display. You can click on them individually and Stop them or use the Stop All feature. Clear this area out of any unwanted background programs and then try the to open KForce again.