I am having I believe the same problem with some pretty expensive systems that I must build and deliver to my customers !!! I am getting a pathetic 75 Win/Sec on wm_torture benchmark utility from RasterMan.
However, based on my numerous testing on different gears, the Dell Precision T5400 Workstation w/ Quadro FX1700 is the one the less affected by the problem (cause it performs the best)
Maybe specific code for that i5400 chipset variation !
My gear is: Tyan Tempest i5400XT, Dual E54XX CPUS, Quadro FX1700 and 9800GTX+
Here is my post for those interested: http://www.nvnews.net/vbulletin/showthread.php?t=131730
St-Nvidia, please pray for us!