Problems using library since upgarde to iTunes 9

I have upgraded my itunes to version 9 on the weekend and have had problems viewing & using my library ever since. When I try to select any of the songs it says it cannot locate the original file and I do not seem to be able to fix it.
I backed up the library to an xml file before the upgrade and have tried to import that back in by deleting the itl files and dragging the back up xml file to the desktop and importing playlist as suggested. All that seems to do is duplicate the standard playlists on the left hand side fo the screen and bring no library items back at all.
Can anybody suggest anything as I don't think I can face reloading all of my CDs again.