First of all make sure you have latest version from ld's site:
http://koponen.home.xs4all.nl/beta/ld_mixer_v1_21.zip and this:
If you replace any existing files, take backups first.
Crashes when you connect anything to it when running multiple sessions of Buzé or Buzz from different folders at the same time.
Crashes when you connect anything to it when running from a directory where the full path has a space in it, e.g C:\Program Files\Buze. (fixed in Buzé 0.4.8!)
Skin doesn't work without Gear\Effects\ld mixer.gfx.