You can try to use the "Polled Mode" instead of IRQ mode in your PCMCIA-FBUS card. The "Polled Mode" will not occupy any IRQ resource, thus there will have no such IRQ sharing problem.
Please close all the NI-FBUS program, especially the NI-FBUS Communications Manager, then run the Interface Configuration Utility, you will see the "Board0", which is your PCMCIA-FBUS card, right-click the "Board0" and choose "Edit". Then the "H1 Interface Board Properties" dialog appears, just click the check box "Polled Mode" to make it checked, close the Interface Configuration Utility, and try to run NI-FBUS software, it should work.
Hope it helps.