I had X1 drop out the sound output on me completely a few months ago. The meters all still showed all of the proper volume levels, but the output was completely dead.  Running the Wave Profiler utility brought it back up. No problems since then, so I'm guessing that Sonar managed to lose touch with the internal sound card somehow.

Thanks guys for all the help,  no wave profiler led me to the Asio panel where I fiddled about and I got the sound back, Yipeee!   Thanks again guys. Danny.