Hi folks,
there seems to be a problem to add folders two times (amarok 2.0.2 (opensuse 11.1)).
Repoduce:
1. Add a folder with mp3s. Update your collection -> mp3s added to collection , fine :-)
2. remove folder and update collection -> mp3s removed from collection. Anlso fine :-)
3. add the folder again, adn update collection -> mp3s are NOT added to collection 

I've got this problem too (Amarok 2.0.2 on Kubuntu Jaunty).

My initial collection  was in /home/bob/Music. Initial scan added all my files.
Later on I added /home/bob/Download to my collection. 'Update Collection' added the contents of that folder to my collection.
Then I removed /home/bob/Download and 'Updated Collection'. This is where strange things started happening:
a) The contents of /home/bob/Download disappeared from my collection (not strange, this one)
b) Other, random albums from /home/bob/Music disappeared from my collection
c) I added /home/bob/Download back to my collection in did 'Update Collection'. The contents of that folder did not reappear in my collection, nor did the other missing albums, but I now have random duplicates of some other albums from /home/bob/Music.

This is completely repeatable. My collection holds about 30,000 files but I never had any problems with Amarok 1.4/MySQL.

The collection scanner is a bit flaky in 2.0.x. Stay tuned for 2.1-beta1, which contains many fixes (also for the scanner).

Great, thanks for the update. I might look at doing an svn build.

Just re-read my post.. 30,000 files??!?! I'm getting my stats confused... 30 days play-time (according to Amarok 1.4)...

Must think before pushing Post button
Must think before pusihng Post button
....