I haven't used Amarok for more than 6 months and the first thing I encountered when I launched it was the missing collection problem, although in my case, it was a lot less complicated than what the others faced. All I did was set up a MySQL database and the problem was solved.
Here's how you can set up a MySQL database for Amarok:
MySQL setup for Amarok Do note that you can use any password you want.
MySQL is a lot faster than SQLite if you've got a huge music collection (like me). So, for those of you out there who are still using the default SQLite, it might be worth the while to switch to MySQL.
Ubuntu 9.04 / Amarok 2 Sound Problem
Exaile - The Amarok Alternative