I can be added to the list of those of you that have been successful in correcting the dreaded Start Menu Crit Error problem by uninstalling Dropbox but I don't like it. I just yesterday uninstalled and will wait a few days to take any further action to see if this really fixed the problem. As I have been looking for a solution for several months now and reading the various tales of whoa, I don't think this step is a cure-all. I would hope DB AND Windows engineers can collaborate to fix this the right way. DB could one-up Windows if they would at least acknowledge this phenomenon. Windows 10 is anything but a 10.
I also have been trying to fix the Start Menu critical error on a Toshiba laptop since it got "upgraded" to W10 from W8.1 in August. Nothing anyone suggested actually worked when I tried it. However I uninstalled DB having read this thread and the start menu has magically reappeared. Let's hope it stays that way!
I have reinstalled Dropbox because I really need it for work, but have disabled autostart with Windows. I will keep you posted if the issue reappears. So far, it has not (about a week).
I am so glad to find this post. I had the Start Menu. Cortana & other Windows Apps stop working on 2 different machines - a desktop I upgraded from Win7 to 10, and a new ASUS Laptop with Win10 pre-installed. It's been driving me crazy trying to figure out what the root cause may be. I too have Dropbox on both machines, but it never occurred to me that it might be involved. Microsoft has been no help - they're workaround was to create a new local user or install Windows 10 fresh. That does provide a workaround, but is not a solution. Now with DB potentially being involved, this is making more sense as I believe DP and the User directory are related, and the problem somehow seems to be related to the User. If it occurs again, I will first try removing DB to see if that fixes it. I hope DB & Microsoft work together to identify the defect and fix it permanently. Of course, this all assumes DB is actually involved and not just a correlation. I wonder if all the users who have experienced this have DB installed.
I have discovered many things in regards to the "Critical Error Start Menu and Cortana aren't working. We'll try fixing it for you the next time you sign in." problem on Windows 10 and honestly as a Computer Repair Tech my coworkers and I have discovered that has nothing to do with Dropbox, if anything it is just a temporary cause.
Many people have thought that Avast Anti-Virus has been the cause for this error because they had Avast and removed it and then the problem was gone for awhile. Some people don't use Avast, like myself and have gotten this error. I happen to use Dropbox and removed it but the Critical Error problem came back a few days later, so it wasn't Dropbox related either.
Some Windows 10 users have said certain updates from Windows Update are the cause but Windows 10 updates are cumulative so removing any update means that the next cumulative updates package released by Microsoft will reinstall any and all updates you are missing on your system. There are no ways to control what updates you install or don't install on Windows 10.
Also, the Windows 10 Critical Error problem has been around since before the release of Windows 10 to the public on July 29th. This error was present/discovered during the Windows 10 Technical Preview but Microsoft never did anything to fix it then, they didn't know what was really the underlying problem causing it and they really still don't.
Yet not everyone gets this error, some people are just unlucky it seems and get it. :(
No argument from me James. In my case there was a trigger event, being the Dropbox suggested upgrade. I tried to report the sequence as dispassionately as possible in case it added to the knowledge around the error. 😊
Incidentally after reinstalling Dropbox for desktop, the error has not recurred in past 5 days.
Wonder what the next trigger might be!
Just as a note, originally my error was "critical error start menu and cortana aren't working." But after I reinstalled Windows 10 (twice!), the error changed to "critical error start menu", no mention of Cortana. Not sure what that means, but it might be useful for anyone trying to figure out the cause. I have been manually starting Dropbox instead of autostarting it with Windows since 11/23/2015 and the issue hasn't reoccurred yet.
Solved!!! Just to confirm that Dropbox (free, personal edition) is indeed the problem for the Windows 10 Start Menu critical error, Cortana not working, the Windows key on the keyboard not working, and right click on Taskbar program icons not working. Whew!
Solved by delinking my Dropbox app from my account, uninstalling both Dropbox and Dropbox Setup (via Programs and Features), and restarting.
Hope this helps.