missing something

hi all, been playing with 9.03 and have a question, as I doubt its a bug, more likely something I have not done. I am building a tank wagon and decided for the next version I make a new tank, use the unwrap and replace the current one. Now I have done that but can not position it before taking out the old one.
According to 3DC the 3 tanks shown in the pict are all at the same position X,Y,Z (except the orange one which I have moved sideways to show)
I have no idea what I have done….

just so its clear, the black tanks the current one, the unwrapped one and the orange are new, smaller one is just a test, so ignore.
[attachment=0:2aqmwnyp]<!– ia0 –>Clipboard01.jpg<!– ia0 –>[/attachment:2aqmwnyp]

<!– s:oops: –><img src="{SMILIES_PATH}/icon_redface.gif" alt=":oops:" title="Embarrassed" /><!– s:oops: –> see I knew it was me, forgot that the black tank was part of a group and therefore the position I had was the group centre rather than just the tank centre, so easy to forget. Shame one could not find the parts postion without moving the group centre back to it <!– s:D –><img src="{SMILIES_PATH}/icon_e_biggrin.gif" alt="" title="Very Happy" /><!– s:D –>