Quadro FX550 dual DVI - one port fails to ...

This is bizarre.

Dell Precision 690 system with dual-head FX550 card. When the OS puts the monitors into power save mode, the monitor connected to the RHS port (looking at the card from the back of the computer) does not recover if it is running at max resolution (1600x1200) *AND* it is running DVI.

If I adapt the port to VGA to connect the monitor, it works fine. If I reduce the resolution to 1200x1024 it works fine. The monitors are Dell 2007FP. I've tried many combinations of settings on both ports but the problem seems to be independently specific to the RHS port of the card.
Trying the "kick the cat to see if it twitches" approach. Would like to understand what is going on and how to repair. Thank you.