I had a similar error while importing a type containing an addnode widget and I had this node after the submission was blocked by requirement that I reported in this other issue #232046: Requirement blocking modification which has a workaround; I don't know if this applies to all instances of the error.

  • warning: call_user_func_array() [function.call-user-func-array]: First argumented is expected to be a valid callback, '1_node_form' was given in /var/alternc/html/m/millette/william/includes/form.inc on line 218.
  • warning: implode() [function.implode]: Bad arguments. in /var/alternc/html/m/millette/william/sites/all/modules/subform_element/subform_element.module on line 211.
  • warning: implode() [function.implode]: Bad arguments. in /var/alternc/html/m/millette/william/sites/all/modules/subform_element/subform_element.module on line 211.