I haven't used auto-bombard, so my answer is all hearsay gleaned from the forums (but hearsay that rings true to my ear nonetheless
![Wink](http://static.apolyton.net/forums/images/smilies/wink.gif)
). If you have checked the preference item "Wake when next to enemy unit" or its equivalent, that preference will override the auto-bombard -- the catapults, set to auto, "wake up" before the auto-move portion of the turn because they are next to an enemy unit. Seems a little silly, but there it is.
Catt