The way I see that passage Scott is this:
God is not actively changing the hearts of the people to a depraved state but leaving their hearts dull EVEN in the presence of sound teaching and the gospel message.
Faith comes by hearing, and hearing by the Word of God but no one can hear unless God quickens the understanding.
So the people would hear the Word that would save but the Lord prevented any kind of quickening. The usually procedure is that God gives the command and gives the ability at the same time. Example: "Stretch out your hand!" But in this passage of Isaiah God is describing how he will give the command but without giving the ability and gives the condition for when he will return to the usual procedure.
[Edited on 31-1-2005 by maxdetail]