After de-installing Microchip Studio and the 2015 shell, then installing Rev. 7.0.2542 as suggested in https://community.atmel.com/foru...
the program starts, produces the initial window completely, then the error message appears:
An exception was encountered while constructing the content of this frame. This information is also logged in "C:\Users\Jerry\AppData\Roaming\Microsoft\AppEnv\14.0\ActivityLog.xml"
If one runs Microchip Studio as administrator the error does not appear and the program runs projects as expected.
It thus looks like this is a file permission problem, but which file?
The system is Windows 10 Home version 20M2, another system with Windows 10 Pro version 1909 does NOT show the error
The activity log from the failing system is attached
Thanks for the help, Jerry