After Banquo's bloody ghost crashes and ruins Macbeth's and Lady Macbeth's formal dinner party and all the guests are hastily sent home, Macbeth is scared and unnerved. He is now desperate to know his future:
I will tomorrow,
And betimes I will, to the weird sisters.
More shall they speak; for now I am bent to know,
By the worst means, the worst. For mine own good
All causes shall give way.
His plan is to visit the witches as soon as possible. He's ready to kill and kill again in order to free himself from the fears that shake him nightly.
Lady Macbeth, who has just witnessed his bizarre behavior at dinner (she didn't see any ghost), thinks maybe her husband is just over-tired; she says, "You lack the season of all natures, sleep."
It's a lot more than that, and she probably knows it by now.
In this scene, Macbeth is starting to lose control of himself. For example, he is seeing visions of Banquo, the man he has had killed. He decides, after seeing these visions, that he needs to go and consult with the witches again the next day. He wants to go and talk to them to find out who might be plotting against him.
As far as what Lady Macbeth says, I'm not sure what you mean by "wrong." She tells the guests that he has had these episodes ever since he was a kid (so they don't think he's going crazy when he starts seeing Banquo's ghost -- he's the only one who can). I think that's probably what you mean.
Banquo's ghost, born of Macbeth's fear-stricken conscience, appears twice at the coronation Banquet, and the feast is abandoned even before it is properly inaugurated.
Macbeth is now concerned about Macduff, and resolves to visit the witches the next day to learn from them more about his future--'by the worst means the worst'. Earlier the witches chose to meet Macbeth, and now Macbeth chooses to meet the 'weird sisters', thus enhancing the impending catastrophe.
Lady Macbeth advises her husband that he needs repose in sleep. Macbeth has been sleepless for a long time, and that might be the reason of his terribly unsettled mind.