We have seen similar issues to this before, and debugging the situation will require meticulous inspection of a NI-Spy file from the driver operation. Typically if an attribute is returned as being invalid, the session you are communicating with is not the session type you expected. So, in the case of an invalid VXI Logical Address, you may be requesting this from a serial port session, for example. Look through the Spy file, and check out all viClose calls and viOpen calls. Resource Manager closings will recursively close sessions below the Resource Manager, and a VISA session ID that has been closed could be opened to a diferent type of instrument further along in the program. You may want to use VISA Interactive Control to help troubleshoot as well. It can hel
p check for valid resources in the system.
Ryan Tamblin
Applications Engineer
National Instruments