After starting the program it displays the usual initial screen but displays the error message:
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".
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.VisualStudio.Shell.Interop.IVsShell5.LoadPackageWithContext(Guid& packageGuid, Int32 reason, Guid& context)
Deinstalling Studio and reinstalling it didn't change the behaviour
An installation on another system and on another disk of the same system worked without error
The latest Windows is installed on all systems
The activity log is attached as a .zip file
Thanks for any help, Jerry