Greetings,
There may be some additional information that is needed in order to understand or troubleshoot the issue. What versions of NI-VXI are being used with the two controllers? Is there any way that you can determine whether the DSP board is actually asserting the interrupt line or not? Have you possibly created any SPY files for the communications?
Answers to these questions may be helpful in determining why there is any issue.
Thanks,
Patrick R.