wow this one is persistent! and if you have seen it you know what im talking about. No amount of scanning with mbam, comboxfix any antivirus software can fix this.
However...
boot into recovery console, log on to your windows installation and type "fixmbr" and all of your problems will go away,
Phew! this one *almost* made me reinstall the computer in question but persistance on my part paid off.
Please leave a comment and say thanks if this helped you :)