Changing GPIB cards from ISA to USB or PCI produces errors in an already working program

[dbnrl]

We have a program written in Visual Basic 6.0 that has been working for many years on machines with AT GPIB/TNT cards but when we tried to upgrade them we needed either PCI or USB GPIB controllers but they have a problem and send an error stating the last command was unrecognized.  The computers are controlling CAMAC crates with a 3998 GPIB controller.  I have tried all types of combinations of operating systems, windows 98, ME, 2000, and XP, 3 different GPIB cards, ISA, PCI, and ISA, and on 4 different computers with and without ISA.  They all produce the same results where the ISA cards work and the USB and PCI don't no matter what operating system was running.  I know they cards are fine because I am able to control other equipment with them.  If anyone could please give me some idea as to why this is doing this.
Thanks

-Doug
 

[dbnrl]

2 mistakes, it is a 3988 GPIB controller and I meant we tried ISA, PCI and USB GPIB controllers.

[markus kossmann]

Could you provide a NI-Spy log of both the working and a non-working case ?

[dbnrl]

Sorry I didn't respond quickly, but I have found that older versions of the 3988 card work with everything, I tried about 6 of the 3988-G2A and 2 of the 3988-G3A.  The NI-Spy logs dont really help as the errors are only seen inside the Byte Status you get from the CAMAC crates and NI-Spy doesn't seem to have an option to display bytes instead of ASCII in the databuffer.  Thanks anyway.