FS2004 Minimizes Itself During Flight - Laptop Running XP??

My FS2004 runs normally on my desktop machine and completes a long flight without problem - running on XP.
However, on my laptop - also running XP - the flight periodically minimizes itself and goes into 'pause' mode leaving me with my normal desktop. Maximize it and press 'P' and the flight resumes from where it had paused itself.
Screensaver is set to 'OFF' - the laptop has more RAM than the desktop and a faster processor and a better video card.
Anyone with a cure for this irritating glitch? Help would sure be much appreciated!