This quote from the OP hit home.

    Me:   The program was written with 3 SQL selects 
    inside a loop. It ran OK when we had 500 parts. 
    Now that we have 10,000 parts, it runs real slow.
    Boss: I don't understand.

I could say "true story" here... with a twist. Saying "I don't understand" is basic social engineering & management 101. The boss actually understood every single word and implication in that statement, he just wants to buy some time to decide silently on the best answer. Saying "I don't understand" puts the pressure on the dev who is lead to believe it's his fault and needs to think of a better description, maybe less technical and more to the point to express the problem. While the dev reformulates, the boss has finished thinking of an answer and can give it instantly. In the end, the dev has managed to express a problem with "simple" words, and the boss has proved he has great skills at solving problems once they are reported in the correct form.

I hated my boss when he did it to me, but I have to admit I used this in turn countless times when I became "the boss", to the point it's become a private joke in my former company, anyone saying "I don't understand", whatever their position, instantly got thrown balls or clips in their face.