The M8190A Software contains examples using visa32.dll in C++, C# and VB. You can find them at C:\Program Files (x86)\Agilent\M8190\Examples. Did you try one of those or did you start from scratch? Another alternative to program the M8190A is to use IVI-COM.
Otherwise, please send an e-mail to email@example.com with a more detailed description of the problem.