I was using GP 2013 just fine this morning. After I restarted my machine I went to launch it again, but before sign-in I get an add-ins error. I do not have any add-ins for this test installation of GP. In considering whether an update was applied I checked and there are VS 2015 Updates (KB 3022398 & 3165756) which were installed today. Yet, I'm uncertain how to prove/disprove whether one is the culprit.
Also, I always keep a zipped copy of the application directory around from its first install and I've unzipped that archive (keep in mind this is a development environment on my laptop) and launched GP again but I receive the same error.
The following is in the Application Event Log:
Choosing to debug:
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