Audio encoding failed...

Had the same problem:

"Audio incoding failed. If Audio is in 2 pass VBR encoding mode, try either CBR or 1 pass encoding."

I basically did exactly what it told me to do. In your Export Settings, under "Audio", change your Bitrate Settings from VBR to CBR (also called "constant bitrate"). It will show encoding passes options, which I just selcted "one". It exported perfectly after that!

I have had exactly the same problem today.  I have never had it before although I have exported using the same parameters on a regular basis.  I am exporting from a 1920 x 1080 x 25 timeline to half res PAL wmv files. 

I assumed that something on the timeline was corrupted, so I switched off the timelines being exported one by one to isolate the problem.  It turned out to be on Audio one.  I checked the audio clips to try and find some error but discovered nothing.  Eventually I moved all the clips on Audio one to another audio timeline and the problem was solved.

It doesn't make any sense, but it worked for me.  Sorry I cannot offer a more rational solution,  I hope this helps?