Hello,
it could it be an incompatibility with the desktop PC (maybe?). I know of cases in which the PCI board can be incompatible with a certain PC for various reasons (PCI bus not 100% compliant to PCI standards, PCI power rails, PCI bus-master capabilities, motherboard/chipset issues, etc..).
I mean, has the PC been changed?
Wich PC model/brand is it?
Have you tested it on another of PC (another model)?
In case you have already tested your mxi-4 in other PCs and the behavior is the same, I suggest you to contact your local NI office for assistance.
Regards,
Jorge M.