Ah - the quirky Poser 5 interface! All sorts of strange things seem to happen to it. Try fixing your problem by going to Edit>General Preferences. Then set it to factory state on both available choices and apply preferred state. Then close Poser and reopen it. One person suggested in a previous thread that going into the default pz3 and setting it to "Read Only" can stop some of these problems, but this hasn't worked perfectly for me.