do you have the plugin published?
components > comprofiler > manage plugins
i have run into oddness when switching smo ajax and this shoutbox, i wanted smo to get the ding on new message but it wouldnt work because i already had this shoutbox running
perhaps it isn't working becuase your shoutbox table was set up by smo ajax shoutbox
try droppingt he shoutbox tables, removing both the module AND the component of the smf shoutbox, then install com and mod for the new box
if that doesnt work then let me know
basically im not sure why but the 2 shoutboxes have a tendancy to interfere even when completely dropped and reinstalled
SoM