I'm sure that it's connected to bug that I've reported 2 months ago: http://issues.ez.no/IssueView.php?Id=10336&activeItem=2
Basic problem is that your form (generated by eZp) does not consist all of fields (input tags with proper name attribute) requiered by eZp. In this case eZp won't give you any error message, just will stay on content/action page and display your form.
My solution was to recreate all objects (forms) after making new class translations, but maybe there are some other things which casues problem.
