MP Control Manager detected NLB MP is not responding to HTTP requests. The http error is %1.%12 Possible cause: MP service ...

%11MP Control Manager detected NLB MP is not responding to HTTP requests.  The http error is %1.%12

Possible cause: MP service is not started or not responding on all MP physical machines. 
Solution: Manually restart the SMS Agent Host service on the MP. 

Possible cause: IIS service is not responding. 
Solution: Manually restart the W3SVC service on the MP.

For more information, refer to Microsoft Knowledge Base article 838891.
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