During the import of ASCII file first line in the file is recognized as a column long name(which is correct). It happened that the name starts with " (double quotes) (i.e. "time). Everything works fine until I have tried to fit a region of data selected with Regional Data Selectior. The region is not recognized: "Data for fitting not specified..." When I remove leading " from the column long name (X-column) everything works fine. This is a bit annoying because no warning or any error messages appeared during naming or renaming X-column.