Version:           2.1.1 (using 4.3.1 (KDE 4.3.1), Arch Linux)
Compiler:          gcc
OS:                Linux (x86_64) release 2.6.30-ARCH

Since 2.0, Amarok messes up the collection randomly sometimes. It switches the album of one music with other, and do the same with the artist.

For example, lets take some albums:
Artist: Mike
-Album: Mike (1996)
--1: Music
--2: Another Music
--3: This is music
-Album: 2 (1999)
--1: New Music
--2: Old Music
--3: No Music
--4: Yes Music
Artist: Juán Caldera
-Album: Las Baladas de Juán (1977)
--1: Baila Conmigo
--2: Besame mucho

It would become like this:
Artist: Mike
-Album: Mike (1977)
--1: Music
--1: Baila Conmigo
--3: This is music
-Album: 2 (1996)
--1: New Music
--2: Another Music
--2: Old Music
--3: No Music
--4: Yes Music

Artist: Unknown
-Album: Unknown
--juan-caldera-besame-mucho.flac

This was just an example. I hope it can clarify things.