**UPDATED** Copssh Control Panel introduced in version 4 has solved that problem. Previous Copssh versions and copsshadm command line tool still have that problem.
This is a known error related to the localized names of the groups administrators and users. There is no solution yet. However, You can use the workaround below:
- Rename localized equivalents of the groups administrators and users to something readable in latin (can be done via Administrative Tools->Computer Management->Local Users and Groups for example)
- Rename the groups above back to their original values.