GX620 Dual LCD Monitor Setup - Blinking Issue

I have a couple of GX620 machines with a 256MB ATI Radeon X600 adapter added for dual monitor setup.  The two LCD monitors (Dell 1906FP) are attached to the video card through a dongle with two DVI inputs (monitors are using supplied DVI cables).  I updated the drivers recently and also tried changing the refresh rate on Mon.1 to 60mhz refresh rate and Mon.2 to 75mhz (I read this on another forum).  Both monitors are set to 1024x768.  The computers and monitors are connected to an outlet that is connected to our central UPS system.  I have tried connecting them to our "regular" outlets with no luck.

 

Here is the problem...

Throughout the day, when the users are working on these computers, they have noticed that the monitors blink.  Only for a second, but they blink.  It doesn't matter what applications are opened or which applications are on one monitor or the other.  It may not happen for a couple of hours or it could start in the morning when they get here and not stop (note: not constantly blinking, maybe a few minutes in between each blink).

 

Any help would be appreciated.  Thanks in advance.