I am currently running 7068. I have had this same problem with versions 7000, 7057, and 7068. When i install a new version, i always format the drive and preform a clean install. When the problem presents itself, I will first try to restore from an image backup i keep on another drive. If that works, i can usually get another week or so before the same problem presents itself. About 50% of the time, the image restore will not solve the problem, and I perform a clean install.
I think you can get to the recovery console by booting to the DVD, then selecting repair computer. That will give you access to the command prompt, though i dont know if fixmbr and fixboot are options there.
I'm not worried at all about losing data, all of the important stuff is either on a different physical drive, on an external backup, or in dropbox. Its a pain needing to reinstall every couple of days, but all i lose is my time.