never heard of the brick either... has to be one of those specific northern thing: winterizing, freezing, noreaster, ice eater, brick.
i woudn't worry about a "brick" just yet, just check the vent, filter and possible valve as i suggested earlier and take it from there.
also, try another pump out. At my marina here, whe the tide is high, it's harder to pump out since the bow is pretty high above the dock. hard for the "stuff" to be sucked 6 or 7' above the dock pump out fitting.