[andi67]

Well the access of the differant Groups is working with Flags , Steamid is stored for clients to save their lasst choises and on reconnect they will become the last Skin they have choosen.....so if Steamid or IP is not the question but are you using admin.cfg or admin_simple.ini ?
Also did you use any other plugin that is setting skins?
Which Version of sm_skinchooser are you using , the latest 1.9?