D2 AJAX working, but Highlighting throws RJS type error null value

And Safari then spews a dialog full of this:( trim for LJ )

Interestingly, as can be seen from the output above the tr is correctly id current-item. The previous round of Ajax changes is working fine, and the cart updates in the sidebar, even when the errors fly. Dev log says:
( trim for LJ )

So, where should I be looking for my typo ? :) I'll go ahead and dump session, restart Safari and script/server again while I wait :D

Thanks,
Posted here: http://forums.pragprog.com/forums/66/topics/1678