google search does only refer to windows vista problems, so I come here to ask ...
 
since one of the recent win10 updates @ boot I sometimes (not always) get the following error from the Microsoft Security Client: "An error has occurred in the program during initialization. If this problem continues, please contact your system administrator" Error code: 0x80070426
 
I reboot it's gone again ...
 
???

That message is probably from Microsoft Security Essentials, which should not be running on Win 10. It should have been replaced by Windows Defender and automatically removed from the system on upgrade. 
 
See if MSE shows up in your list of programs in your uninstallation window and if so try to delete it there or:
https://scottiestech.info/2016/04/30/windows-10-cant-uninstall-microsoft-security-essentials-no-problem/
 

thanks, but I never had Security Essentials installed (just doubled checked) ... hence fix provided in that link does not apply
 
there is again a bunch on win10 updates available. i'll go ahead and update and see if this error goes away (as it came with one of the updates some 2 months after I upgraded to win10)

I did a quick search and it can be multiple problems, not just the old Windows Security Essentials.
A Windows activation issue, Windows mail problem, Software licensing service, etc.
 
If you don't get it resolved with the updates, post the problem on the Windows 10 forum (3rd party forum not Microsoft).  www.tenforums.com
 

fireberd
I did a quick search and it can be multiple problems, not just the old Windows Security Essentials.
A Windows activation issue, Windows mail problem, Software licensing service, etc.
 
If you don't get it resolved with the updates, post the problem on the Windows 10 forum (3rd party forum not Microsoft).  www.tenforums.com
 

thanks for taking the time to look into this. i'll check out tenforums