Hello EborLance,
The NI-4551 can use either NI-DAQ or NI-DSA as the driver. If you only have NI-DAQ installed, any program that uses the NI-DSA functions may be crashing.
There is no direct mapping of NI-DAQ functions to NI-DSA functions but you can download and install the NI-DSA driver from the website.
Current DSA Drivers Once you have installed the NI-DSA driver, you should see the functionality you were previously used to and your program should run.
Thanks,
C. Flip
National Instruments