Bertie, I had this problem when I used Pinnacle. It seems to conflict with the sound card driver I was using. I don't know exactly how or why it did this as I'm not a software expert. My sound card was a DMX6fire. when I reverted back to the motherboard sound card this worked. You might also check out if you have the ASIO4ALL audio driver which caused someone a problem. Just a couple of ideas that may help.