In the latest EAP there is the problem with parsing and detecting errors in xml files described with the XML schemas.
I've attached the little project here. Before any actions you have to add the Idea Options->Resources the following entry: "urn:schemas-dig-de:test2" with the link to the "test2.xsd" file.
Than, if you open test2.xml the "test2:control" will be highlighted as of it is incorrect (though the xhtml1-transitional.xsd has been updated to allow the "test2" namespace's elements to be in ]]> tag (see line 401 in xhtml1-transitional.xsd).
By the way, the rest in the area of XML schemas looks much better than in the release 4.5.
P.s.: after editing of any xml files they have to be saved. Otherways the EAP things there are some bugs inside of these XMLs...