Using the last beta version of ME Pro for testing.
I don't know if this is a known problem. Using OE6 to connect to the WebDAV service, wich works great. But when I have multiple mails and I want to mark them as read (or unread) i get this message from the server:
The Professional install kit on our web site has been updated with this fix. You can see a list of changes by either heading to our support or download web page.