Problem with export function

[Edu_loco]

I've tryed sometimes convert videos recorded in AVI to MP4 using function export ( videos only recorded by mirillis action ).
Export config : 720p (High) If I open the video in media player classic for example the video run normal with Video/Audio, but if I import in sony vegas only audio come :/. But this not happens all time, if I export many times the same video it can work one time o.O the problem is the time, because export finish in 8 ~ 15 minutes :/

You know what I can do to solve this problem?
Thanks for all help.
Sorry for bad English.

[radi]

Could you post your video exporting settings?