Amarok 2.1.1 wasn't building a full collection database, so when I looked further i noticed that amarokcollectionscanner segfaults on some m4a files I have.  They are the only m4a files I have, so I can't confirm whether this is a general m4a problem or not.  Segfault is:

0x0418af9c in TagLib::MP4::Tag::parseBool(TagLib::MP4::Atom*, TagLib::File*) () from /usr/lib/libtag-extras.so.0

Does anyone else see this?  Or is it a bleeding edge fedora problem?

I have also tried to view the tags on these files in easytag, and it doesn't like the files either (it doesn't crash, but displays no tags).

On the other hand, mp3tag (windows) works fine and displays all tags correctly.

My environment is:

fedora rawhide (fc12)
amarok 2.1.1
taglib 1.5
taglib-extras 0.1.4

Seems similar to this reported bug: https://bugs.kde.org/show_bug.cgi?id=197782

Same problem here.
Error log: Faulting application amarokcollectionscanner.exe, version 0.0.0.0, time stamp 0x4a2723be, faulting module tag-extras.dll, version 0.0.0.0, time stamp 0x4a2715ab, exception code 0xc0000005, fault offset 0x00005d9f, process id 0x1890, application start time 0x01ca0f8b9e3f3e00.

I am able to add some of the M4A files to the playlist  and play them. But this only works for some of the  M4A files.

Problem is restricted to windows (Amarok on linux works fine for M4A files)