Well this is not really a bug, just something nasty.

I'm using amarok 1.4.0 with KDE 3.5.2, on kubuntu (build date May 18 2006)

I love the moodbar cause it's something that i don't really need but it looks fine.

First, with normal use, i load a playlist, and start to play it.
If the moodbar hasn't been calculated, the computation is done at the beginning and then, the moodbar is displayed. Good.

Now, i want to play a little more with amarok , and decide to show the column "Moodbar" (in french "Humeur") in the playlist window.
Result : all the moodbar are loaded if they exist. If not, amarok queue all the jobs for the computation of the moodbars of the tracks present in the playlist. These jobs don't appear in the "waiting queue manager" ("gestionnaire de file d'attente").
You can erase your playlist, the jobs remain queued. You have no way to prevent the calculation of moodbar to be done, except by killing/quiting amarok.

I would like to stress that moodbar calculation is extensive RAM and CPU consuming processes, and having this done on an "old" computer (my computer cpu is an athlon 1800+, and with 520 MB RAM), with a "big" playlist (more than 20), can be hell.
I've tested this on my entire collection (a little less of 12000 tracks), and after a few hours, amarok sucks all the RAM and all the CPU time. Kwin is generally the first program to complain it hasn't any memory left ....

If i could suggest something, it would be to trigger the moodbar calculation only when a track is read. otherwise, keep the "Moodbar" column empty for the track. 

Sorry for my broken english.

Yeah, it's a known.

In the meantime, better to only use moodbar on the progress slider, where it's calculated on a per track basis.