Divx video stuttering, 720p works?!?

[HD23]

Hello, I use Aviaddxsubs to make avi files into divx files with subtitels supported by the PS3. Those files are not HD quality with regular stereo sound but they always stutter and impossible to watch. When I play M2TS files with 720p they play great with excellent quality and 5.1 sound. When I play those files in MKV they also stutter.
I have an AMD 3000+ processor and a wireless 2.5m cable network. I tried diffrent Media servers and stick to this one because its the best but I had the same problem with all of them. Im aware its probebly a network error but why 720P plays and regular SD dosent?
Any help would be great! Thank you!