This is SMELLING like a OS X issue!!! Have not encountered the Static Screen of Death 1x with the Dell 3007wfp-hc display attached to the Windows Media Center PC all evening. By this time, I would have lost sync at least 2-3x. Remember - this is a 4870 1GB flashed with Apple firmware. This card had sync issues on the MacPro. It's not a cable issue either.... Sooo....
MacPro OS/X Specific Behavior:
DVI-DL port: Monitor looses sync and causes the image to be intermixed with a static image. Happens within minutes of the machine returning from sleep. Happens more often, if the image on the screen is not changed and remains static. Can be corrected powering off/on display.
MDP -> Apple MDP->DVI-DL Adapter: On occasion after wake from sleep, will "pulse" to static image every 20 seconds or so. Can be corrected by unplugging/plugging DVI cable into MDP/DVI-DL adapter.
Windows PC Behavior:
No issues to report. I feel cheated!