When using the DVI output of a video card into a flat-screen LCD panel, there is an occasional flicker, especially when there is hard drive activity, and sometimes the screen goes completely blank for a couple of seconds.
The solution is to change the refresh frequency of the display output to something higher. In my case, I changed it from 60Hz to 75Hz and now the display is fine. To do this, right-click on a spare area of the desktop, select properties. Click on Settings tab, then Advanced button. Click on Monitor tab and change the drop-down list to a higher frequency. Note: it's useful to confirm that this has actually happened by using the on-screen display of your monitor to check the frequency being used, before and after changing it.
If it isn't changing, or no other rates are available, install the correct driver for your MONITOR.