This error message manifests on Administrator Forms for many non-core extensions even when an item has been selected.
This backwards compatibility error will be fixed in core for 2.5.1.
- Install the plugin from this forum item 
- To address this problem now so that your users do not have to wait for a core fix, update your Administrator forms and change name="adminForm" to id="adminForm". If backwards compatibility is required, simply use both values in the form definition. In future releases, Joomla will only support id="adminForm"
A patch has been created to fix the backwards compatibility in 2.5.1