I've had this problem since the nightly builds. Everytime I try to scan my music folder the progress bar stops around the 75~77%, then I get no error messages. When I re-open amarok, some of the musics are there, but most of them are missing. I'm having this problem using ubuntu 8.10 and also, yesterday, I tried it with a Mandriva 2009 Live CD but got the same issue.
Edit: Forgot to say that Amarok 1.4 works fine.

Well, see here:

http://bugs.kde.org/show_bug.cgi?id=176154

I read everything, but could not find anything related to my problem. In my case, Amarok is importing a good amount of my songs and I can play then, but looks like it stops the scanning process suddenly before the end.