An error has occurred while trying to access the license validation key file. Please reinstall SQL Server to correct the file ?

I'm getting this error following installing SQL 2008 on a Windows 2008 R2 OS when trying to open SQL studio, can anyone offer explanation why this is occurring ?  I have installed SQL 2008 SP1.

I see many others have also had this issue but cannot find a documented solution and/or confirm reason as to why it occurs.