Some additional debugging information:

If I run Notation Composer without launching Garritan Personal Orchestra it still crashes within 3 to 5 minutes of launching Notation, so it doesn't have to do with GPO. It usually begins by becoming unresponsive when I try to drag a mod wheel curve. I click and drag and nothing happens, although the mouse pointer still moves. When it crashes during playback it usually begins by freezing on the last note played, sometimes starting again before crashing ans sometimes just crashing from the frozen state.

About 50% of the time I get a message for my video card just before it crashes saying that my video card has become unresponsive and that I need to reboot to reset it. (ATI Radeon 9600) I downloaded and installed the latest video drivers with no difference. Notation still crashes within a few minutes of launch.

CTL-ALT_DEL to bring up the task manager often shows Notation as "Not Responding", but then sometimes it will begin responding again before the whole system crashes.

I'm running P4 3.2 GHz Windows XP Home, 1 GB RAM.

Hope that info helps.

--gary shannon