I get this error message about 50% of the time when rendering. "The palyback device Microsoft Sound Mapper does not support the current output format. The playback device Microsoft Sound Mapper does not exist.
It only happens about half the time and I can restart Vegas and render successfully after a failure. I've tried using Direct Sound Mapper instead but my render failed with no error message when I did that. I also have the Windows Classic Wave Driver and Realtek ASIO as options but didn't try them.