Is this McHost, or McSvHost? They're two different McAfee services, and the problem will have a different cause depending on which one you mean.
Ahem to that comment.
Mchost.exe error caused by having alcohol 120% software installed easy fix available
Mcsvhost error can be helped by disabling netguard a firewall feature. A fix coming in a couple of weeks it have been held up due to a bug or 3 in another fix included in the patch.