HI Steff,
The problem with this VI could be that it does not explicitly specify which decimal point character should be used by the "Scan From String" function. By default, the node uses LabVIEW's default decimal point, which is either the system decimal point or the period (if "Use localized decimal point" is not selected). If you know that your text contains one type of decimal point character, you should explicitly state so on the format string using the "%" formating directive.
The problem can be fixed by explicitly specifying the decimal point in the "format string" of Scan from String function.
Hope this helps.
Regards,
Pravin Borade
Applications Engineer, National Instruments