(Summary: The problem in my case turned out to be a simple dependency on user account folder locations. The path to the Documents folder changed, and Audition freaked out. Why Windows saw fit to blame it on MSVCR120.dll, I'm not sure. For the full story, read the whole post.)
I'm posting this here, in case anyone else encounters this same issue. I'm also hoping this information makes its way to the appropriate people in tech support, so that they can better understand how to deal with the problem. If my experience is any indication, TSR's are painfully under-informed on this problem. As soon as the one I spoke with saw in the Event Viewer that MSVCR120.dll was involved, he told me the only solution would be complete, clean reinstall of my OS. My exact reply was "WHAT???!!!" There was no way I was about to do anything that drastic, just because one single dll file was throwing a tantrum.
I knew there had to be a far simpler fix, and it turned out I was right. After some Googling, a whole bunch of trial and error, and a bit of good old fashioned observational analysis, I discovered both the cause of the problem and the solution. Read on.
Poking around via Google revealed that corruption of MSVCR120.dll is not at all uncommon, and often causes crashes with quite a few applications. The recommended fix in most is to reinstall the Visual C++ Redistributable, so that was the first thing I tried. No dice, however; Audition kept right on crashing. So, from there I went on to try just about every potential cure I could think of, from deleting preferences folders, to complete uninstall/reinstall of Audition, to full removal and reinstallation of drivers, to registry cleanup, and on to about a bazillion other things that would take too long to list. But none of these made Audition any happier.
Then I noticed something. One of my hard drives wasn't showing up in Explorer. (There are six internal drives in this machine and three external ones, so the absence of just the one had been all too easy to overlook.) A bit of testing of the drive in question showed that it had suffered a mechanical failure, and quietly died. Not cool! But obviously, the timing was too much of a coincidence. The two issues had to have been related. Now the question was what might have been on that drive that Audition wanted badly enough to make it refuse to start when it couldn't find it?
Easy answer: My Documents folder was on that drive. (Did I mention not cool?)
Even easier new theory: If Audition's only real problem was that it was upset about not being able to find the Documents folder, then the problem must have been linked to the user account. So, as a quick test, I relogged under a different account, and Bob's your uncle, it worked! Theory confirmed.
Now the only thing left to do was to go back into my main profile, and assign a new location for Documents, right? Well, not quite. Windows didn't want to let me do it, for some reason. The Location tab was notably missing from the Properties dialog on the Documents link. So, I did the next logical thing. I simply reassigned the letter of one of my other drives to the letter from the dead one, put a new folder on it called "Documents", and presto-abracadabra-alakazam... Audition started right up, without complaint.
So, what's the moral of the story here, kids? Well, it goes like this. Audition is basically a stalker, with big old giant crush on our girl, Documents. He constantly keeps is eye on the path to where she lives. He NEEDS to know she's there at the end of that path, or he gets all kinds of crazy depressed, and refuses to go to work. And the pair of binoculars he uses to spy on her has "MSVCR120.dll" written on the side.
Also, as is the case with most stalkers, Audition's obsession with Documents is purely superficial. He doesn't know or care in the slightest what she's got on the inside. As a folder, Documents can be completely empty, and Audition won't even notice. All he's concerned with is that she's got the right name, and that she lives at the end of the right path. That's it, and that's all, as far as he's concerned.
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Esteemed Adobe TSR's, if you're reading this, here's the takeaway. The next time someone calls you because Audition won't start due to a fault with MSVCR120.dll, please suggest that they switch user accounts BEFORE you suggest that they go ahead and wipe their entire system. As my story shows, the customer's problem might very well just be that Audition is looking for paths that are no longer correct. And that's super easy to fix.
If nothing else, please at least take from this that wiping out the OS is NEVER the first answer, no matter what the problem. There's ALWAYS something else to try first.
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If anyone's curious, the OS in question in my case is Windows 7 Ultimate. The Audition version is CC 2015, build 8.0.0.192.
Thanks for reading. Replies, comments, welcome.