--- Operating System, Graphics card ---
Windows 7 x64
nVidia 460gtx


--- Blender version with error, and version that worked ---


--- Short description of error ---
Kind of minor but it is repeatable on my Windows 7 system.
Add audio to the VSE.
Now setup a MPEG render so the intention is to render a video with audio.
Now choose an audio codec that does not match the target MP4 container, such as MPEG video and PCM audio.
Issue a render and Blender will claim that there is a mismatch between the audio and video codecs which is correct.
However, behind the scenes, Blender has already opened the file for rendering and is still holding on to the file handle.
Now correct your mistake of choosing PCM and set it to AAC audio.
Issue a re-render and everything goes along fine....until you view the final output.(which is invalid or nothing).

What seems to be happening is that even though the video and audio codecs are now valid for rendering, the file can not be re-opened because Blender still has a handle to it. So Blender goes through the motion of rendering the full frame but can not store the results in the file Because it is already open.


--- Steps for others to reproduce the error (preferably based on attached .blend file) ---