Instant replay stutters

Hi,I was wondering after getting some trouble with stutters appearing when I replay my flights in FS9 if this issue may be explained by a recent installation of a new video card driver and directX 9.c.What surprises me is that these stutters only appear while "instant replay" function is running. As soon as the replay begins, a couple of stutters appear, then disappear and the movie get back as fluid as you may hope.One point I have noticed is that each stutter is accompanied by an access to the hard drive whose light is turned on.Has anybody already experienced this ? What do you suggest ? Your help is welcome.Kind regards,Vincent Mellinger