From: Cardiff / Wales
i used to have the same problems with a creative geforce 2 graphic card...
i know that this will sound strange, but the white screen problem and the upside/down problem is a result of faulty or damaged graphic driver... If there is any way to disable and enable again overlay modes, you will see that the video won't be upside down...
But, just to be sure, you can try bsplayer first (it's free). Load the avi file with bsaplayer and disable overlays or disable RGB mode (which one is enabled) in preferences menus... if the video displays ok, then you can try transcoding the files again... If none of these works, then you got yourself some damaged avis... try divxfix in this case... and cross your fingers...