Windows 8.1 Update 4/25/14 'can't access profile'

Hello all.
Friday night when I came home from work I got the notice that I had updates and the computer would reboot on it's own in 24 hours. So I just went ahead and did the reboot. When it finally came up... it took a long time, maybe 20 minutes or more... I got the message that it could not find my desktop profile, and that access was denied.
None of my icons were showing on either the desktop or the taskbar, and when I went to the Windows 8 Start screen, many of my icons were missing from there, too (including IE, ironically). Google Chrome would not open. So I rolled back to before I did the install, (when I got the message that the undo didn't work either and I should turn off my AV). The third time was the charm, and I appear to be safely back to where I was Thursday.
However, in looking around to see what was going on here, I see that there was an update I had to have "or else ". That may have been a prior update, I'm not sure how to verify that.
So:
1. How do I know if I got the 'must have' update or not?
2. What went wrong with this update and what, if anything, should I do about it?
Thx.

 

Microsoft.com > Windows 8.1 Update (KB2919355)

 

Thanks, Spyware, but I don't know what that means in this context. Cumulative sounds like each update is inclusive of all the ones that went before it, rather than incrementally only updating things that are new since the last update. Is that what is meant here?
If so, then I can skip this update and take the next one, right?
But that still doesn't tell me what went wrong this time or what to do about it.
**update**
I looked in PC Settings and turned off automatic updates. I also see that the update that ******* me has been downloaded again and is set for automatic restart in 24 hours. Will that still happen even though I turned off automatic updates? The number of the offending update is KB32919355.

 

I was merely confirming the fact that the "Windows 8.1 Update ", aka KB2919355, is a "must have" update. Think of it like a forced Service Pack. "All future security and nonsecurity updates for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 require this update to be installed in order to receive continued future updates. "

See this page, especially the Notes under How to obtain this update, the Known issues and the Prerequisites sections: Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 Update: April 2014

Even more here: Install the latest Windows 8.1 Update