Hi,
  This is triggered by series of action for me:
  1. select 1 or more m4a files
  2. edit track details
  3. make a change to a arbitrary field, and press 'save and close'
    SVN checked out in 4/29. KDE 4.2.2. Gentoo, built with GCC 4.3.3
    To build it by portage or manual way doesn't make difference.

  A backtrace is attached, please ask for any further details if needed.
Thanks.

Please check http://bugs.kde.org for existing reports. If you find one add your backtrace, otherwise file a new report.