MSScriptControl:Unknown Error

It may help to know a bit more about your operating environment (i.e., specific system model, recent changes to configuration, recent problems/virus activity, etc.), but the first thing I'd suggest is to read through this conference (as well as the Special Interest - Virus/Spyware Information and Removal conference) for information on malware insofar as what it is, how to identify it and how to remove it.  You should also make sure that your anti-virus application is up to date, and that you've run a recent scan of the whole system to rule out the chance of any virus activity.  I'm inclined to think that the problem may be more related to malware though, so you might want to consider installing and running (after reviewing the user guides for same following installation) something like AdAware and/or Spybot Search and Destroy, to make sure you don't have anything on the system that's responsible for that message, as malware appears to be a frequent cause.

Assuming you're able to rule out virus and/or malware activity as the cause, another option would be to perform a System Restore to a date prior to when this problem showed up.  Your onboard Help and Support application will offer detailed information about System Restore and how to use it.