Synopsis: Troubles combining UseCanonicalName with DirectoryIndex State-Changed-From-To: open->closed State-Changed-By: marc State-Changed-When: Fri Feb 11 12:22:11 PST 2000 State-Changed-Why: You have it backwards here; the canonical name is what the server thinks it is, not what the client does. You want UseCanonicalName off.
That still won't deal with the port issue, so for that you need to make sure you set a "Port 80" directive and use a "Listen 8080" directive to tell Apache to actually listen to port 8080, while thinking it is on port 80. Note that the example URL you give won't show this problem, because you include a trailing '/'. It only will if you don't include the trailing '/'.