This is a new problem, noted within this month, I would say- after recent update or one update prior. My VST scan starts scanning and then stops on selected plugin- different every time, and does not progress. Right now it stopped on Z3TA+2. Last night it was something else. If I restart Sonar, it scans and then hangs on different plugin every time.
 
There few other issues I noted- for example it asks me to verify Sessional Drummer- cant remember what it says but it gives me drop box to select Session Drummer from it. Weird. The other day Reactor was shown as crashed and offered to disable. Ok- I assume- this can happen. It loads ok today. Another time I decided to use "Rescan" for all plugins because I installed few new plugins and they were not on the list. So the VST Scan flagged all SoniVox VSTs as being not registered. Ok- I did clone my C drive some time ago so they could become unregistered due to change in hardware, but the serials are stored on iLok, so it should not matter. The iLok plugins should work on any computer. It said to open iLok and then restart Sonar, so today it works.
 
Those are all minor irritating every day struggles I learned to put up with but I need to know why the VST Scan hangs. Looks like it never finishes, I don't see "Scan completed. 750 plugins found, 0 new". I like to get updates on how many plugins I have (and yes, according to Sonar, it is over 700). It usually tells me that it found new plugin if I installed something. But now it just fails to finish. Thank you.

You should probably subscribe to this forum submission. It is a Microsoft update caused problem! http://forum.cakewalk.com/FindPost/3530846

I'm on Windows 7 64bit and have the very same symptoms with the 2016.12 Early Access.  Not sure if the MS update that's been previously mentioned is a factor in my case.
 
I'm hoping they correct this (and some other issues) before the final release of 2016.12.
 
Later,
Paul

Thank you for the reference. I am reading the thread you recommended.
 
This time scan completed and it says, 750 plugins found, 560 are new. I will assure you I did not install 560 plugins.
 
It says Izotope Stutter can not find the files and to reinstall.
 
It says AirMusic plugins need iLok drivers to be installed. Why would it ask this if iLok software is ok? Will try to update drivers.

Ok, I think I fixed iLok issue. But it still freezing on random plugins. And it often "thinking" while scanning, not sure if it reading some plugin information. But I have many plugins and I see it thinking often. Also I got unusual drop outs of audio when audio is not even playing.