I attempted to run an TestStand 3.1 Sequence file on my new computer in TestStand 4. And I had a 17502; system level expection run time error for a particular function call. The sequence access the function or module from a .dll that was developed in LabWindows/CVI 7. However, this code module works on my other station that runs TestStand 3.1. I also attached the example of the code that's causing this run-time error in TestStand 4.
Most likely you are getting an access violation in your C code. Have you tried stepping through your C code in the CVI debugger to see where the error is happening?
I did step through the code to see which function call was causing error. However, when I save the sequence file at a TestStand 4.0 sequence file and executed the sequence this system level exception error did not occur again.
Do you still have the 3.0 file? Let us know if you are able to reproduce the problem again.