well, here goes..
I bought a Carvin Icon about a year ago, and I've got a couple frets that are 'dead'. Not meaning that they buzz, but the have zero sustain. I counted. a regular fret got to about 40 seconds of sustain, the dead ones have about 3 seconds.

So... whats up? It sounds like they are muted by something.
Oh, one more thing: they are only on the g-string. Yes, I changed out the strings a couple times, no solution. This leads me to think it may be a tuner or saddle issue.