There quite a few possible causes for the error; it would help if you could give us some detailed history of the problem such as when it started occuring and what (if any) hardware or software changes you made at about that point.
The following links cover many possible scenarios, but perhaps one will help with your particular situation:
http://www.google.com/search?hl=en&l...29&btnG=Search
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Wombat At Large
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since Dec 2003
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