Urs:
This seems odd and I have not heard of this recently. You should run the Measurement & Automation Explorer, which also calls VISA to find resources. If that crashes, then re-run MAX and it should tell you what search was current at the time of the crash, and let you disable that specific resource.
As an example of where I do remember this happening, it was where some specific serial port was used for some special device that VISA needed to ignore. Disabling that one port solved that specific problem.
If that does not help, please use NI Spy to capture the calls and send the resulting log file to our tech support.
Dan Mondrik
Senior Software Engineer, VISA
National Instruments