Then was king Belshazzar greatly troubled - Not doubting that this was a Divine intimation of some fearful event, and yet unable to understand its meaning. We are quite as likely to be troubled by what is merely "mysterious" in regard to the future - by anything that gives us some undefined foreboding - as we are by what is really formidable when we know what it is. In the latter case, we know the worst; we can make some preparation for it; we can feel assured that when that is past, all is past that we fear - but who can guard himself, or prepare himself, when what is dreaded is undefined as well as awful; when we know not how to meet it, or how long it may endure, or how terrific and wide may be the sweep of its desolation?
And his countenance was changed in him - Margin, "brightnesses." See the note at Daniel 5:6.
And his lords were astonied - Amazed. The Chaldee word means to perplex, disturb, trouble. They were doubtless as much perplexed and troubled as the king himself.

Then was King Belshazzar greatly troubled,.... A second time, and perhaps more than before; since he had conceived some hope that his wise men would have informed him what this writing was, and the meaning of it; but finding that they were nonplussed by it, it gave him still greater uneasiness:
and his countenance was changed in him; again; very likely, upon the coming in of the wise men, he had a little recovered himself, and became more composed and serene; which appeared in his countenance; but, upon this disappointment, his countenance changed again, and he turned pale, and looked ghastly:
and his lords were astonished; were in the utmost consternation and confusion, when they understood that the writing could neither be read nor interpreted; neither the dignity of their station, nor their numbers, nor their liquor, could keep up their spirits; so that the king had not one with him, to speak a comfortable word to him, or give him any advice in this his time of distress; they were all in the same condition with himself.

By this not only was the astonishment of the king heightened, but the officers of state also were put into confusion. "In משׁתּבּשׁין lies not merely the idea of consternation, but of confusion, of great commotion in the assembly" (Hitzig). The whole company was thrown into confusion. The magnates spoke without intelligence, and were perplexed about the matter.
Not only was the tumult that arose from the loud confused talk of the king and the nobles heard by those who were there present, but the queen-mother, who was living in the palace, the wife of Nebuchadnezzar, also heard it and went into the banqueting hall. As soon as she perceived the cause of the commotion, she directed the attention of her royal son to Daniel, who in the days of his father Nebuchadnezzar had already, as an interpreter of dreams and of mysteries, shown that the spirit of the holy gods dwelt in him (Daniel 5:10-12).