Hello,
the Problem is solved:
Are you using the DAQmx Create Scale vi as well? It is actually not possible to create a scale with the same name as an existing scale. However, you can still modify and save an already existing scale. For an example of how to do this, check out the following link: http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=F38DB14830876FE6E0340003BA7CCD71&p_node=201209&p_source=External
Thanks a lot.