Version:           2.1.1 (using 4.2.2 (KDE 4.2.2), Kubuntu packages)
Compiler:          cc
OS:                Linux (x86_64) release 2.6.28-13-generic

These seems to happen every day or two:

I look at the amarok window and see that "Multiple background tasks are running", and the progress bar is sitting at 13%. If I expand the view to see what the tasks are, I see six (6) instances of "generating playlist".

According to "top" amarok doesn't seem actually to be doing anything, and even if I wait for hours, the progress meter doesn't change and the "Multiple background tasks running" message never goes away.

The only thing I seem to be able to do is simply hit the "Abort all background operations" button. That works... until the next time the message appears.