Update from my experience with this problem:
I guessed that the problem had to do with some incompatibility with Win8.1, so I upgraded to Win10. This was not without its own difficulties, but once installed, I tried to open TT Business (Partnership/Trust) which failed as before, but with a different error message. Under Win10, I uninstalled and then reinstalled the program, and this all went without an issue. Beyond creating several returns, I've not yet operated the program itself, but I expect it's okay. I then opened TT Personal (Schedule C) and it downloaded updates and operated correctly. So I believe I'm back in business.
From the nature of the initial error I received under Win10 (which forced the un-install), I suspect the root cause of this is the Win8.1 updater is a 32bit code and the Win8.1 I was running was for 64bit. This is something that TT will need to investigate further ... it cost me about a week of time.
