Just got the SV-1 back from a Korg service center. The key needed to be replaced. They weren't really sure what caused it, but its back and good as new now. I was still covered under warranty, so it didn't cost me a thing.
Same thing just happened to me last night. The Bb above middle C just collapsed. I've had mine for about a year as well. Going to try to get in touch with Sweetwater and/or Korg today. I'll let you know if I have any luck.