Sorry, my formatting above sucked, been using JIRA too much :)

The key difference is the `"id"=>"22"` in the `group_parameters_attributes` section.

This may be as simple as changing "param.clone" to "param.dup"

https://gist.github.com/ericsaboia/994614

Confirmed in "develop" (1.8) .. and in debug mode, it also confirms that its crapping out on the group_parameter.

2015-03-18 11:56:46 [I] Started POST "/hostgroups" for 10.250.251.1 at 2015-03-18 11:56:46 -0600
2015-03-18 11:56:46 [I] Processing by HostgroupsController#create as HTML
2015-03-18 11:56:46 [I]   Parameters: {"utf8"=>"✓", "authenticity_token"=>"Y5APgFaxM+tTlwuDK7Dk7J9c4PG1EThzagazKfMX8V0=", "hostgroup"=>{"parent_id"=>"", "name"=>"Cloned", "environment_id"=>"1", "compute_profile_id"=>"1", "puppetclass_ids"=>[""], "domain_id"=>"1", "realm_id"=>"", "architecture_id"=>"1", "operatingsystem_id"=>"1", "medium_id"=>"1", "ptable_id"=>"7", "root_pass"=>"[FILTERED]", "group_parameters_attributes"=>{"0"=>{"name"=>"TestParam1", "value"=>"[FILTERED]", "hidden_value"=>"[FILTERED]", "_destroy"=>"false", "nested"=>"", "id"=>"1"}}, "location_ids"=>["", "1"], "organization_ids"=>["", "2"], "id"=>""}, "commit"=>"Submit"}
2015-03-18 11:56:46 [D]   User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", 3]]
2015-03-18 11:56:46 [D] Setting current user thread-local variable to admin
2015-03-18 11:56:46 [D]    (0.1ms)  SELECT COUNT(*) FROM "taxonomies" WHERE "taxonomies"."type" IN ('Organization')
2015-03-18 11:56:46 [D] Setting current organization thread-local variable to none
2015-03-18 11:56:46 [D]    (0.1ms)  SELECT COUNT(*) FROM "taxonomies" WHERE "taxonomies"."type" IN ('Location')
2015-03-18 11:56:46 [D] Setting current location thread-local variable to none
2015-03-18 11:56:46 [D]   AuthSource Load (0.4ms)  SELECT "auth_sources".* FROM "auth_sources" WHERE "auth_sources"."id" = 1 LIMIT 1
2015-03-18 11:56:46 [D]    (0.1ms)  SELECT id FROM "taxonomies" WHERE "taxonomies"."type" IN ('Location') LIMIT 1
2015-03-18 11:56:46 [D]    (0.1ms)  SELECT id FROM "taxonomies" WHERE "taxonomies"."type" IN ('Organization') LIMIT 1
2015-03-18 11:56:46 [D]   Taxonomy Load (0.1ms)  SELECT "taxonomies".* FROM "taxonomies" WHERE "taxonomies"."id" = ? ORDER BY title LIMIT 1  [["id", 1]]
2015-03-18 11:56:46 [D]   Taxonomy Load (0.1ms)  SELECT "taxonomies".* FROM "taxonomies" WHERE "taxonomies"."id" = ? ORDER BY title LIMIT 1  [["id", 2]]
2015-03-18 11:56:46 [D]   GroupParameter Load (0.2ms)  SELECT "parameters".* FROM "parameters" WHERE "parameters"."type" IN ('GroupParameter') AND "parameters"."reference_id" IS NULL AND "parameters"."id" IN (1) ORDER BY parameters.name
2015-03-18 11:56:46 [D] not found: Couldn't find GroupParameter with ID=1 for Hostgroup with ID=
2015-03-18 11:56:46 [I]   Rendered common/404.html.erb within layouts/application (1.8ms)
2015-03-18 11:56:46 [I]   Rendered layouts/base.html.erb (112.9ms)
2015-03-18 11:56:46 [I] Completed 404 Not Found in 135.5ms (Views: 117.5ms | ActiveRecord: 1.4ms)