The Bees have now lost five league games in succession without scoring a goal in any of them.
Ruthless Butcher rang the changes by dropping three players in the shape of Lee Thorpe, Sammy Moore and Glenn Poole and for a while it looked like working as Brentford started brightly with Ryan Dickson seeing a good effort saved before Charlie Ide's cross shot was deflected just wide by Nick Fenton.
Brentford were well and truly on top as Ross Montague headed Gary Smith's free-kick just over and Alan Connell had a shot blocked by Robert Atkinson after a fine through ball from Ben Starosta.
But Danny North served Brentford a reminder of the danger down at the other end by forcing Simon Brown into a fine save before missing a sitter in front of a gaping goal.
Down the other end, rookie striker Montague forced a brilliant save from Phil Barnes in the Grimsby goal before North again forced Brown into a fine save.
Brown had to be in top form again just after the break making a brilliant one-handed save from Nick Hegarty's header and from the resulting corner Karleigh Osborne cleared off the line from Atkinson.
However, after surviving that scare, Brentford failed to learn from it and North took advantage to give the visitors the lead on 56 minutes.
Brentford rallied and a brilliant Smith shot was saved by Barnes before O'Connor just failed to connect with an Ide cross.
But O'Connor had to be alert at the other end too to clear his lines with Gary Jones waiting to pounce.
Thorpe, Moore and Ricky Shakes all came on as Butcher rang the changes and Thorpe had a header saved before seeing a shot cleared off the line as time ran out.
But that was as good as it got for Brentford and Butcher's position as manager now looks precarious with yet another protest from fans after the game.