I have escalated this to our regional helpdesk also.
I have noticed the error has appeared on another machine overnight. I have a feeling it could be related to a license issue within the software.
It is affecting all preflight presets and the optimise node. the preflights were the standard "fix ups".
I couldn't wait any longer for a resolution or explanation. I went ahead and ran Install repair. I bypassed the installers desire to reinstall Visual Studio 2010.
Preflight is again functioning.