Updates start up for me, also. Updated to new apps, ran Word and signed out of personal account and into non-profit account, and all apps (Office, Word, Excel, PowerPoint) all startup with the non-profit credentials successfully.
The quick fix, development of the problem with the RC, and somewhat sporadic nature (worked for some and not for others) makes me wonder if it was an uninitialized variable (or similar). When the debug code for the betas is removed, sometimes these problems can appear.