Here is one that had me pulling my hair out a bit.

Have iMac mid-2011, which has been happily running Office 2011 for years.

Last year our company tried Adobe CC, which was a nightmare: its desktop installer/updater constantly conflicting with OSX ( messing up permissions) and crashing constantly with EVERY update (which were numerous). Finally after many wasted hours and fruitless uninstalls, cleanings, re-installs we have pulled the plug on Adobe forever - cancelled our CC subscription and have found excellent alternative (non-adobe) media editors to actually GET SOME WORK DONE.

But the aftermath of the Adobe headache was substantial, the machine was basically crippled from all that OS corruption that Adobe had inflicted on it. The Apple techs gave up after several hours and suggested the best fix would be a complete WIPE and fresh clean install of OSX. OK!

But as luck would have it, there was some glitch with the Apple servers last week, and it literally was six days ( and several hours with tech support) to get an Apple OS installed. No kidding! And all it would finally offer when it did connect, was OSX "Lion"! But beggars not bein' choosers, that was downloaded, installed, and duly upgraded to 10.10.4 without further incident.

So... a bunch of applications to install, the first being Office 2011. Ran the installer, and within the hour it was installed. Software update suggested a critical office update (14.5.1, i think) and though we had had numerous issues with its immediate predecessors, I somewhat rashly decided to install it. OK!

Then opened up Outlook and proceeded to hook up my five exchange accounts. But NOT SO FAST... actually, it won't connect with ANY exchange account. I tried several, and every case it refused to complete the account setup, citing bad username or password. Checked with my Exchange provider, they were puzzled. They tested the same accounts locally, and had no problem. Seems the issue was with my workstation! 

Undaunted... I did that careful Multi-step "complete office 2011 uninstall" that is documented online. Rebooted, and re-installed office 2011. This time - DID NOT INSTALL THE OFFICE UPDATE! And  guess what? No problem connecting up my Exchange accounts now!

I imagine that after I get all my accounts in, it will 'probably' be safe to apply that pesky Office Security patch. As we eventually had it working (with some grief) the last time. But I'm going to wait till all my mail loads, and run the full backup FIRST.

Just thought I would share this, in case someone else might have the same situation in the future!