I have the same problem. Windows 7 Professional (32-Bit), Factory installed onto a 3Ghz. 64-Bit AMD Athlon II x2 model B24.
I also noticed the output file is sent to my desktop and does not save the video thumbnail preview until the second save as per the above post #3. Also the framerate, video size, and bitrate are not saved to the file header the first time. After pulling in the video to "Blender 2.72b" the audio data is listed with the video, but it is not present , the devs have written something in the output header but forgot to write the actual audio data the header points to.
Check the size of the first file and second file, they differ in size due to the alocated (in the header) but missing audio track.
The above workaround (post #3) is OK for small clips of video, but larger sized clips or full races take ages to complete.