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

[adric]

And Safari then spews a dialog full of this:
Element.update("cart", ..LJ can't handle this, please link through to forum.. );
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:

Processing StoreController#add_to_cart (for 127.0.0.1 at 2008-12-29 07:10:10) [POST]
  Session ID: 725832306db6b01f7c809916443ddf60
  Parameters: {"commit"=>"Add Sandworms of Dune to Cart", 
"authenticity_token"=>"34e7bc3aa8ad32f2cf977ccaa1c5da92b22a3ac3", "id"=>"602372474"}
  Product Load (0.4ms)   SELECT * FROM "products" WHERE ("products"."id" = 602372474) 
Debug: cart: add_product: @current_item is 
Debug: cart#add_product returning #
Debug: store_controller: @current_item is #
Rendering store/add_to_cart
Debug: _cart: #
Debug: _cart_item: # @current_item: #
Rendered store/_cart_item (4.6ms)
Debug: _cart_item: # @current_item: #
Rendered store/_cart_item (0.8ms)
Rendered store/_cart (7.7ms)
Completed in 15ms (View: 11, DB: 2) | 200 OK [http://localhost/store/add_to_cart/602372474]

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