S4Czech:

The audio fix stopped all my problems. 

Start, Control Panel, Sound, Right Click SPIDIF Interface, Properties, Advanced(tab), and then.....

UNCHECK "Allow applications to take exclusive control of this device"

The audio change fixed by video problems.

Thanks

My system is as follows:

Motherboard - ASUS AT3N7A-I MINI-ITX Intel Atom N330 NVIDIA Ion DDR2 GBLAN HDMI Audio BT Motherboard
RAM - Corsair XMS2 TWIN2X2048-6400C4 2GB 2X1GB PC2-6400 DDR2-800 CL 4-4-4-12 240PIN Dual Channel Memory
HardDrive - Hitachi Deskstar HD31000 IDK/7K 1TB SATA 7200RPM 32MB Cache 3.5IN Hard Drive Retail Box
NTSC tuner - Hauppauge WinTV-PVR-500
ATSC tuner - Hauppauge WINTV-HVR-950Q TV Stick External USB2.0 TV Tuner NTSC/ATSC Digital HDTV (I disabled the NTSC tuner in Win7's hardware/device manager)
BluRay/HD-DVD reader - LiteOn ??? model
Case - Apex MI-100 MINI-ITX Case Piano Black 1X5.25 1X3.5 Sfx 250W Front Audio USB

Running Win7 Home Premium. Driving out via HDMI.

Playback on my system was causing my display to blank out for a couple of seconds. This was quite periodic at 7-8 minutes when playing back video and after playback (such as surfing the net), every 20 minute or so the display continued to blank. Please note that the only foreground operation is playback of either .avi, .mkv, or .wmv file. No other processor intensive application are running either in the foreground or background.

 >Start, Control Panel, Sound, Right Click SPIDIF Interface, Properties, Advanced(tab), and then.....UNCHECK "Allow applications to take exclusive control of this device"

I tried the fix above and it seemd to fix the problem. But, after a couple of days, the issue came back. I also noticed that my microphone input also had "Allow applications to take exculsive control of this device" and I unchecked that. But, it didn't work as the screen blanking continues. I have enough free memory (500MB-700MB) so, likely not due to a memory swap.

 Any other thoughts on what could be causing display issues?

I found at least one reason why the image would go black while during playback or just using the computer in general. It turns out that this occured only after I had previously played back a H.264 (all of my material is 1080p) file. The work around is to reboot the computer and no issue.