Okay, this was something that both I and Nadnerb were looking at, and he wanted to see if it was consistant before adding it possibly to his Wiki tutorial on Adding Sounds.
Here is the problem:
I've found that, when you have added several sound files to your Age, everything works like a champ and exports fine.
Now, save your .blend file and close down Blender. Go have dinner, watch TV, whatever, continue on with Real Life.
Later, or the next day, sit down and open Blender back up, load up your Age's .blend file, do some more work of some sort, like adding some other objects and texturing them, or something.
Now go to re-export the Age to check out your new stuff in Uru...........uh oh, I'm getting and export Error. Say's it can't find a certain sound file.
Sure enough, if you change one of your screens to the Audio Window, and click on the up/down window to see what sound files are loaded, if you have more than one, you'll find the others "missing" for some reason. Sometimes it's just one, sometimes (if you have like 5) it's missing 3 of the 5.
If you turn around and re-open up each of the wav files, the Age will export just fine, no "Missing File" error.
However, this happens to me, every single time I save my blend file, and then shut down Blender, and go else where. When I load everything back up, some or many of the sound files will be missing from the Audio Window, and I'll get a Missing File error upon export.
Okay, easy fix, just remember to check to make sure all your sound files are there when you go to export......
BUT....what happens when you've got a HUGE age, with a LOT of sound files down the road? I guess one answer is to write down a list of all the files on paper and tape it next to your screen, so you can double check each time.......
But, I think this problem will need to be looked at in the future.