When you add a word to the dictionary using the spell checker it will create or add to the orion.dct file in the same path from which you are launching oriondesktop.exe.  This would be O:\orion\orwin in the most common scenario but could also be the local C: in some citrix environments.  If you are getting errors when trying to add a word it could be that the user has lost rights to modify that file. 

To check the user rights browse to the folder and right click on the orion.dct file.  Now go to the security tab.  Here you could have a general name of “users” and give full control.  You could also see your network login name here and would need to give full control to that as well.  The shortcut if your IT’s security will allow it is to click edit, then add, type in Everyone in the “Enter the object names to select” box, and press ok.  Check the full control box for the “Everyone” User now.

Press apply and then OK.  You should now be able to add a word to the dictionary.