I tried going from 1.4.1-beta1 back to 1.4 and now amarok fails to start. Not even an error, it just silently terminates after the usual "do no run gdb on amarok!" message. I do see the splash screen though.

Any clues? Am I stuck with 1.4.1-beta1 (and its messed up UI layout)?

make sure the plugins are removed, and failing that, just do rm -rf /opt/kde/share/apps/amarok
and then the configs, and then the same in your home dir.

The database persistant table version was bumped, you will need to delete the database and start afresh (or just stay with 1.4.1)

I just remembered I did a backup of my amarok config dir a few days ago. Whew!

The lesson here is: ALWAYS backup your amarok database before upgrading! If it's not the upgrading, it's the DOWNgrading that'll destroy your database.