First of all when rendering in maya NEVER render to .avi. Now what you do is in the render globals choose to render out to targa (.tga) and then set the naming convention to "name.#.ext".
Specify wich frame is to be your first (presumably frame 1) and your end frame. Last set framepadding to 4.
When you've done this go under your render tab and choose "batch render". This will make maya render out all of the frames in your animation.
After all of the frames have been rendered use VirtualDub (found at http://www.virtualdub.org/
In virtualdub choose "open video file" and choose the first frame of your animation. Now you can play or scrub through your animation and see that it looks ok.
To get this into a avi just press ctrl+p and choose your prefered compression type (the best being xvid), press ok and then under file choose "save as avi" and your done. :attn:
That took a while to write so I hope it helps.