I was trying to do it since long time.
I was able to stream avi to PS3 using Nero Media Server, but some time it use to give me troubles like skipping frames and jamming for some time.
Yesterday I tried to copy avi file to PS3(You have to copy it by using nero media server) and then play it from HD and surprisingly it worked. Actually PS3 dose support avi playback from hard drive but surprisingly Sony never revealed this feature.
I think you need to enable Divx playback in PS3 setting since it uses Divx codec to play avi. Also it will show avi clip as Divx under Video.
I would try to add video later today.