Hello i have a problem with jEdit / xml plugin

I want to validate xhtml documents with jEdit. I installed the XML-plugin and the required plugins (error list and the others) and everythings is going all right when I start jEdit. To test the function I'm opening a xhtml-file, which has some errors in it. But in the error-list there are no errors displayed. I think it has something to do with the DTD? The xhtml-DTD is in the first line of the file but I think it's not automatically dedected?

Thanx for help

Ralph