From the description you are providing it seems like there is a DMA problem with the 6533 on that computer. This is basically why the board is not able to sustain High rates.
The 6533 is fine since you said it works in another Computer
-You say that the application is fine beacuse it has been working for over 5 years on other machines. Were these machines Dual Processor also?
- You might want to upgrade to the latest :
NI-DAQ Driver Version- You may also want to try and disable one of the processors and see what happens.
Regards,
AlessioD
National Instruments