>There is MS Connect item
>
>https://connect.microsoft.com/SQLServer/feedback/details/573771/value-cannot-be-null
>
>For the first problem, check if https://support.microsoft.com/en-us/kb/955648 may offer any help.

Yes, after more investigation, there was also a cleanup disk space procedure. The Temp in there got removed. SQL Server will not create it, for whatever it needs under that branch, on entering. Only a new login would resolve that.