Bad beam emitter piece issue

[legacy-Melaneus]

I am trying to make a beam weapon effect, but after setting the beam's draw style from brighten to alpha, the first piece of the beam doen't work right. It is black (the rest is red) and lingers longer than the rest of the beam:
http://users.adelphia.net/~csdgames/images/badbeam1.jpg
http://users.adelphia.net/~csdgames/images/badbeam.jpg
Does anyone know what could cause this?