Pixel noise, 30 inch monitor, ATI Radeon HD 5770

I'm running a...

Mac Pro (Mid 2010)

ATI Radeon HD 5770 1024 MB

2 x 2.4 GHz Quad-Core Intel Xeon

12 GB 1066 MHz DDR3 ECC

I am seeing green pixel noise in the dark areas. I thought it was the monitor (HP ZR30W), so did HP, but now I have a new NEC PA302W and--guess what--same problem. This time I searched for the card (ATI Radeon HD 5770) and I see some mention of similar problems but nothing definitive. Any ideas?