Hi,
I have Ubuntu 8.04 and am running Amarok 1.4.9.1 and using KDE 3.5.9.
I'm having some trouble making Amarok work, I'm pretty sure (but not positive) that I've installed all of the codecs that I should have. I added my music but alot of it isn't showing up. Well, correction, it IS showing up, but most of it is classified as Unknown. However, if I go to Edit Track Information, the right information shows up, it is just mostly (at least 3/4 of my collection) classified as unknown even though the program knows what it is from what I can see in the Track Information. Also, these Unknown songs DO play. However, now that I'm looking through all of the unknowns, I think I may be missing some songs/artists too (Amarok didn't recognize them, I guess). Does anybody have any resolution to this problem??? Thanks in advance!

Try to rescan your collection (Tools->Rescan collection).
If this does not help, you could try to delete ~/.kde/share/apps/amarok and ~/.kde/share/config/amarokrc and start over from scratch (however, doing this you will lose all your configuration, ratings etc).