Can you explain what you want to do in more detail?
Several approaches come to mind. You can use velocity envelopes set to zero for pauses and just keyframe a lot. You can play around with the video rate. You can have multiple layers of video with the bottom layer say a quater second behind and then blend them.
If you mean like a strobe and/or ghostly trails effect, try Pixelan SpiceFilters (not SpiceMaster). You could do it in Vegas by cutting up the event you would like to stutter and copy the same frame the desired freeze length. I hope you understand what I mean.
Best/Tommy