Lots of unusual options, but I don't see anything that is glaringly wrong. Any of the options without an entry (level1 file extensions, wins server, etc) should probably be removed (make a backup first), but that probably won't affect your particular issue.

Try this. Edit /etc/gdm/PostSession/Default again and include an explicit unmount for the mp3s like this:
Code:
#!/bin/sh
umount /mnt/mp3s
/etc/init.d/umountnfs.sh

PATH="/usr/bin/X11:/usr/X11R6/bin:/opt/X11R6/bin:$PATH:/bin:/usr/bin"
OLD_IFS=$IFS

gdmwhich () {
  COMMAND="$1"
  OUTPUT=
  IFS=:
  for dir in $PATH
  do
    if test -x "$dir/$COMMAND" ; then
      if test "x$OUTPUT" = "x" ; then
        OUTPUT="$dir/$COMMAND"
      fi
    fi
  done
  IFS=$OLD_IFS
  echo "$OUTPUT"
}

exit 0