After r3563, if you pass an :id key via the :params hash the controller receives :id as nil. See for instance this log:
Start rendering component ({:params=>{:center_id=>10, :id=>25}, :action=>"supervisory_commissions_widget"}):
Processing EmployeeController#supervisory_commissions_widget (for 127.0.0.1 at 2006-04-10 22:07:27) [GET]
Session ID: 94a1e0400481a317fcd235c1360c82ac
Parameters: {"action"=>"supervisory_commissions_widget", "id"=>nil, "controller"=>"employee", "center_id"=>10}
This is a side-effect of a change in the way some local hashes are updated in request_for_component. The attached patch, code and test, fixes this and uses code inspired by url_for.