What errro are you getting during the start.
I ask because we see this from time to time, and we never have to delete the the DB - but hunt down and remove a port group in vCenter that has been left behind. Wondering if it is the same issue.
(Many times a VSE does not shutdown fast, so it gets left behind. So the portgroup delete can not be done - so... it is just left, and until cleared by hand a vapp will not be able to start)