Pro Tools stop playback when I click on any other program

I am running Pro Tools LE 8.04 on Windows 7 with an ASUS 210 Silent video card (nvidia chipset) with 2 monitors. I can use Pro Tools across both monitors without any issue. However, if I click on any other program during playback, the Pro Tools session looses sound and displays "Pause" in the lower left corner. If I stop the playback and try to restart, it displays "Pause" and will not play or record. If I go to Setup --> Playback Engine and reset the H/W Buffer Size it will work again (until I click on another program). I have also tried changing DAE Playback Buffers and turning on/off Low Latency Monitoring but neither helped. I am presuming it has to do with the video card because if I only run 1 monitor, it will work without any problem. I have tried uninstalling the video driver and reinstalling the updated driver but that didn't help. Anyone know to make this work? Thanks. Kirk