I have the soft strap, too. It worked great for about a year and then started giving erratic readings all the time. 200+ BPM while just starting off, etc. Tried gel, tightening it, moving it around, new battery, etc. Nothing worked.

I finally got a tip on one of the Garmin forums to just hand wash the strap (not the HRM unit itself) in warm water with a couple drops of laundry soap. I did that, rinsed it with cold water, and let it dry. Works like a champ again!

Clif notes: The strap itself is probably caked in sweat, salt, and other nasty stuff. Wash it!

Bob