Hello,
unfortunately, the form.get.head.ftl is useless (empty) in Alfresco 4.2, so you actually have not included the necessary dependencies anymore. You should adapt any custom component to the new style of web scripts that no longer have a .head.ftl - especially if you want to use the Forms API. Then you can include the new file form.dependencies.inc which contains all the relevant imports. There are also form.css.ftl and form.js.ftl with (about) the same dependencies - I am not sure which one will stay with us in the long run though.
Regards
Axel