Hi Joe,
I have exactly the same problem.
I’m on an HPZ400, Matrox RTX2, Radeon4870, Premiere Pro CS4.
Years ago I had this problem on a Premiere 6 running with DVStorm and NVIDIA display card. Using the NVIDIA ‘span’ setting for the dual monitors (instead of extended desktop) cured it.
If someone has a fix or workaround for Joe’s problem, please let me know!
Pete