In the banquet scene in Macbeth, what complaint does Macbeth make about murdered men? Is there anything humorous or ridiculous in the complaint?Act...

I presume you are referring to these lines from Act 3 scene 4:

Blood hath been shed ere now, i' the olden time,
Ere humane statute purg'd the gentle weal;
Ay, and since too, murders have been perform'd
Too terrible for the ear: the time has been,
That, when the brains were out, the man would die,
And there an end; but now they rise again,
With twenty mortal murders on their crowns,
And push us from our stools: this is more strange
Than such a murder is.

I hadn't really considered them as comic before, but looking now, I can see a potential for a comic reading if one were to paraphrase them in part by saying something to the effect of

--back in the good ole days murdered people stayed dead--if you bashed thier brains out that was the end--now here they come with twenty gaping head wounds and knock you off your seat.

Though I can see the potential for a humorous reading, I am still not conviced that this is meant to be funny.  I think Shakepeare  is showing Macbeth's shock at seeing the ghost and how is guilt is affecting his mental state more than making light of murder.

Macbeth is so frightened/shocked by the apparition that he forgets himself and speaks openly of the murder in front of his guests.

His mention of being knocked of his stool probably referrs to Banquo's sons becoming heirs to the throne--they will unseat him and his line. 

For an act by act analysis and a modern translation, see the links below: