Dell UltraSharp 2408WFP monitors blink on DisplayPort connection

Hello,

I have a total of 8 Dell UltraSharp 2408WFP monitors, and all are experiencing the same issue.  They all blink (though not necessarily at the same time) once in a while when using the DisplayPort connection to drive them.  When hooked to the same PC and video card via DVI, or a passive DP-DVI adapter, they do not experience the issue.

Initially, I had the monitors hooked to a HIS Radeon HD6850, and the blinking was very frequency (once every 5 minutes or so).  I have changed to a different video card (XFX Radeon HD6770) and the blinking is less frequent (maybe once every 30 minutes) but still annoying.  I have tried new cables and another PC, yet the issue persists.  Changing to the DVI input of the monitor immediately makes the issue stop occurring.  Again, all of these monitors experience the problem, so I don't believe it's a one-off defective unit.

When the monitor "blinks" (goes black) I see the input logo appear for a second when it returns, which makes me think the monitor is losing sync of some sort.  Searching through the forum, I see a few mentions of issues which sound similar, but no one ever seems to have a solution.  Is anyone else experiencing this?  Is there a solution?  Driving all the monitors off DVI is not an acceptable solution as most video cards, such as mine, can only drive 2 monitors via DVI with passive DP converters, meaning I will need to purchase several expensive (~$75) active DP-DVI converters.

Thanks!