Class 37 triple header on a mixed freight

[Gatso]

Three class 37's working hard to pull a mixed freight out of Dumfries. I know the consist is totally unrealistic but feel the power of those 37's.

Can anyone who posts videos here tell me why there's always stuttering around a minute into the video? At 1:22 it happens for a few seconds and this is common with all the video's I've recorded using FRAPS. It's not as if my system is slow - i7 920 @ 3.5ghz, GTX570, 6GB DDR3, SSD hard drive.

http://www.youtube.com/watch?v=Jcf9p4Syzpc