VirtualDub and Divx Compression in reverse ops

[VIDEOHOUND]

Something wierd is happening. When I capture a video file using VirtualDub using Planar MPEG Raw "YUV9" and then try to edit the file with VirtualDub using DIVX or Huffy the file size increases greatly instead of decreasing. What the He?? is going on with this. It is like the compression is running in reverse of what it should be doing.