For more detail I would use the ReportingEvents.log to get the timestamp. Then find the portion of CBS.log which corresponded to that. It might give a clue about which module is "missing".
Hello Robert,
thanks for this great hint!
Checking CBS.log revealed that KB3000850 is picky about the structure of the start menu...
I had moved several entries to a sub-directory:
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessibility
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories\Tablet PC
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories\System Tools
It is easy to spot these errors in CBS.log: search for ", Error" without the quotes (the comma space in front is important).
After recreating these three directories I was able to install KB3000850 :-)
Thanks again & greetings from Germany,
Uwe