Translation:Can you fly?
Ah, darn. Oh well, one often learns a language best by trying - and making errors. :-)
I find it hard to believe there is no Klingon noun meaning 'dream'! But, I suppose I should have taken a clue from the fact that both sources I checked list it as a verb, but not as a noun. Although, your own boQwI' does give the example qul naj, a noun (and famous Klingon novel) meaning 'The Dream of the Fire' (3 separate sources) - meaning that we do have one canonical literary example. (Of course, literary examples are subject to artistic influences and potential language evolution over time, and thus, are not suitable as actual grammatical rules.) :-)
At any rate, pending any further discussion of qul naj, I'll make a note of all of this. qatlho', David, for your amazing boQwI' app!
Real world explanation: The English version came first, using a noun that doesn't appear in Klingon, so a change had to be made.
Fictional world explanation: People change titles of works all the time to better fit the style of the target language, because an audience using that language will not find it awkward or odd. In English it is far more common to use a noun phrase as a title than a sentence, so it should be no surprise that the translator of qul naj chose to turn the title into a noun phrase.
jIyaj! It's still interesting that there is no noun for 'dream'. And, of course, we're talking about an English translation of a Klingon title, really. Nevertheless, this is all good information for a student of Klingon to know, so I'm still glad I asked - and glad I made the original error that brought us to this conversation! There is always worth in errors. :-)