Source Recorder Problem

Hi,

I am trying to create an add for my server using the source recorder, but when I create the AVI video using the “startmovie moviename avi” command, it shows up in windows movie maker with a huge green box covering the bottom half of the video.

I tried lowering the codec capturing quality (because it was quite high) in the box that pops up once you enter the startmovie command, but that crashes my gmod.

Is there any way to stop this green box?

Specs!:
Intel® Core2 Duo CPU @ 2.00GHz
3 GB RAM