1. VST Wrapper 3 has proven to be much more stable with DP than older versions. Try to get the latest version.
2. Allocate more RAM to Digital Performer. Start with a Preferred size of 120,000(k). If you're attempting to use VST instruments, try a preferred size of 150,000.
3. Check to see if a VST plugin is causing the problem. Pull ALL the VST plugins from the VST plugins folder...except for one. See if DP has problems. Then add one more VST plugin, and continue testing DP. See if you can find ONE VST plugin that is causing the problem *(you'll need to QUIT DP before adding a VST plugin to the VST plugins folder).