Just to update. Garmin sent me a new GSC10 . Since in the meantime I had gotten used to riding without speed, I just set it aside (while awaiting delivery of my new bike). When my new bike arrived (beginning of May), I put the new GSC10 on it, and everything was working fine - until last week. It still registers the cadence, speed and distance, except that the speed and distance are off, by a significant amount. All of a sudden, it showed my commute to work as 10.5 miles, whereas it's been showing up as 14.3 miles for over a year (since I started commuting). My speed doesn't seem to exceed 12 or 13 mph, even though the elapsed time and known distance result in an overall average of a little over 16 mph. I haven't had a chance to play around with it, re-pair it, or even post a similar question on the Garmin forum. Hopefully I'll get a chance this weekend. Anyone else have similar problems? Suggestions?

Honestly, I'm about done with this Garmin. When it works it's great, but it seems very unreliable. Lately almost every ride has at least one or two spikes where it says I exceeded 99 mph (I'm not that fast, the tailwinds aren't that strong, and the downhills aren't that steep).