I've had the problem a couple of times now. It's a stutter at about three seconds intervals; so bad as to prevent flying until FS9 is exited and re booted. On both occasions it's been during a flight, or after a flight, having been on the PilotClub server for a couple of hours, On both occasions I've been using the on line weather, so I don't know whether the problem comes from being connected or that plus the weather. To confirm it's not just present when I run FS9 I've left it running, same aircraft, but not on line and with no weather loaded. No stutters.
Any ideas or any fellow sufferers. Gerry Winskill