When either the BOTH or GRAPH option is used, the semivariogram information will be written to an output INFO file called out_grid.SVG. If this file does not exist, it will be created. If it already exists, the new results will be appended. This error will occur if an attempt to write to an existing file fails, perhaps as a result of being locked by another ArcMap or ArcCatalog session.
Ensure that the out_grid.SVG INFO datafile is not write-protected.