Many have experienced the same or similar problems as you with the SBLive cards. Some say that disabling SB16 or legacy emulation (not sure which as I have an Audigy) in the control solves the problem. Others have reported that it doesn't for them.
A few in my squad that have SBLive cards work fine for a while and then lose the ability to transmit and sometimes the ability to hear also.
I had a lot of trouble with my Audigy for a while. I tried so many things so many times, including 3 different motherboards, that I'm not sure what finally made it stable. While it seems unlikely, it's seems to have been affected most when I got a usb joystick and stopped using the gameport. Like yours, mine always worked fine in the windows recorder.