How often are you seeing this error? It's fairly common to get an error about rules occasionally, but if you are seeing them
persistently there could be an issue. Also, if you are running a Control Center, does the scanner show as accessible in the main page on the User Interface? You would want to make sure that your rules show as up to date.
Since this is an error about rules, it may be a corrupted rule set. If this is the case, we can clean up the rule sets through a support call and hopefully that would resolve the error.
Hope this helps.
Tom