The region to polygon tool in toolbox does not work with coverages. The geoprocessing tool does not grab all of the data necessary for creating polygons out of regions. The command regiontopoly in workstation creates polygons in a coverage dataset from regions inside that dataset. Part of the script tries to grab information from the info folder associatied with the coverage. In DT the tool only works with the data in the coverage file itself and not the info folder. This flags the error invalid argument. This tool needs to look for all of the information regarding the coverage to work. The only work around is to execute this in workstation.