Hi John,
The .Net installer has been moved to "Control Panel -> Programs and Features -> Turn Windows Features on or off".
There is an entry for both 4.5 and 3.5 (which contains 3.0 and 2.0). Probably worth taking both..
The error helpfully doesn't say what the object was meant to be, anything in event viewer? Although it does talk about attempting to write a log file, wonder if it is some strange authorisations/UAC issue? Try running as admin?
Oli