I've had continuous problems with my GSC10 speed/cadence sensor dropping out on rides. It connects just fine but drops out for 30 secs every 1-2 minutes. I believe the sensor is fine b/c it has no issues staying connected to my old FR305. My HRM for the 920XT stays connected without issues as well. I've read on the forum about some issues with WIFI interference but I've had the same issue out of WIFI range. Every couple of minutes my watch vibrates with a "Spd/Cad connected" message.
Any help would be greatly appreciated as it's really messing up the data on my indoor rides.
http://connect.garmin.com/modern/activity/675585447