Workbook Open and Activate not functioning

Running 2016. Today two changes that I know of occurred: W10 upgraded to 160610-1700 and I installed the Dropbox client.

Either today or yesterday, after a Windows update and restart (I believe another occurred yesterday of some type), for some time (perhaps 10 minutes) I could not access any Office program - any attempt resulted in a window stating that Office was busy, I believe running updates.

Coincidentally I now find my Workbook_Open event, Workbook_Activate event and WorkSheet_Activate events are not running.

I checked Application.EnableEvents, setting that to True on WorkBook_BeforeClose (which I verified runs with a messagebox planted in it), then after opening the workbook again I simply checked the status of EnableEvents in the immediate window, verified True.

I have verified WorkBook_Open is not running with both Stop and Msgbox commands.

I have further run a complete reboot (btw, after the recent Windows "upgrade" the Start menu refused to come up so I had to nuke the computer (OFF switch)).

Anything else I can check?

Anything else that could cause this behavior?

Edit: Just went to another networked computer that had not had the updates nor DropBox run on it and the workbook ran fine from it. Going to uninstall Dropbox and see if that has any affect on this computer-

Yet another edit: I don't get it. I uninstalled DropBox and the events ran correctly. I did a reboot, all still good. I reinstalled Dropbox and still the events ran fine. Then I did a reboot and the events would NOT run. Last, I ran an uninstall of DropBox (including registry entries via IOBit's "PowerUninstall). Once uninstalled, without reboot, the events in Excel were running once again.

Just now an FYI for anyone else out there-

Might be worth checking on answers.microsoft.com - I had the problem with the start button not working a while ago and I seem to remember there was some mention of dropbox causing a problem so may be worth taking a look. You may also find other people on there who are having similar Excel problems to yours since the latest update.

I was one of the lucky ones and managed to roll back my Windows 10 install to Windows 8 when MS couldn't seem to come up with a sensible solution to the start button issue!