ah , I don't think you can render out of maya to an AVI at anything but 29.97 , thats got to be your problem. AVIs out of maya are a bad way to go anyway. If you render out an image sequence then take it into a post utility you should have 25 frames a sec.
Unless you can get into the avi options ( which I don't beleive you can in Maya ) then you can't tell it what compressor if any to use , what frame rate and other options that are needed .
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