Hi Klaus-
When upgrading versions of LabVIEW, you need to be careful of installing two versions of the same driver on 1 machine. LabVIEW comes with the option of installing the GPIB, DAQ, VISA drivers, etc. If you did not uninstall any of these components and then installed another version on top, this could cause problems - especailly if you are making DAQ / GPIB calls in your program.
good luck
ben