GPIB Communication in Visual Basic 2008 under Win7

Hello

I have a measurement program in Visual Basic 2008 that communicates over GPIB with the instruments. This runs fine under Windows XP.

Under Windows 7 I have no built-in GPIB card but an USB/GPIB adapter. I checked the communication with "Agilent Communication Tester" and it worked, but the measurement program cannot build up a communication.

In the debugger I have found that the constructor for the GPIB driver fails. I can chose one out of two driver DLLs: "LangInt.dll" and "Ivi.Visa.Interop.dll". Both of them fail.

Are these DLLs not suitable for Windows 7 or for the USB/GPIB adapter? Which driver should I use else?

Thanks RR