Contractors are mercenaries. Professionals who serve not out of loyalty, but for money. Since they really have no direct interest in the company's success or failure, then the best that you can hope for is their pride in workmanship or interest in being invited back. I'm not saying that this is bad. It's just the way that it is.
When serving as a manager, I'd generally rather gnaw my right arm off than to use contractor support. I've only used them to perform specialized external services (e.g., dosimetry, anti-Cs, HEPA leak checks, very specialized calculations). This is just a personal choice. I know plenty of successful managers who rely heavilly on contractor support. In their organizations, I know several contractors who do better work and are more reliable than the house employees. In those cases, my question is always "Why are they contractors? Hire them already." Then again, I've never had to manage an outage.
Companies, like nations, decide on the full-time staffing that they wish to maintain. If you don't value your military enough to staff it well for times of trouble, then you hire mercenaries for those times. Most historians agree, however, that over-reliance on this practice was a symptom, if not a direct cause of the fall of Rome. That's what saddens me so much about all of this Blackwater stuff going on in Iraq these days. If a bean counter runs the numbers, and decides that they only need a certain staffing level until an outage occours, then the company deserves what it gets.
In answer to the original question, you shut up an annoying contractor the same way that you shut up anyone else. Be direct. Inform them that they are annoying you, and ask them to stop. If that doesn't work, then let them go, so that they have the opportunity to share their expertise elsewhere. If you can't let them go because they're invaluable, then shame on your organization for putting itself in a spot where its success relies on a single irreplacable individual's support. Put up with it for the moment and fix it ASAP. By the way, this advice applies evenly to in-house collegues as well as contractors.
Let the smiting begin,
MGM