Kubbel Ending Study

I have just completed the Kubbel Ending Study on Chess Mentor.  

After a number of moves the position above is reached.  At this point I tried 1. Qd2+.  I was told this was incorrect.  1. ... Kc5 is forced any other move leads quickly to mate.  Then 2. Qe2+.  From here any of 2. ... Kb4; 2. ... Kb6; or 2. ... Ka5 allows my knight to give check with a discovered attack on the queen.  Chess mentor, however, suggests 2. ... Nd3 which clears the c5 square for his fleeing king.  So Chess mentor gives 3. Qxd3 Kc5 and leaves the analysis there suggesting I try again.  But I had seen this continuation and had planned 4. Qa3+ which, so far as I can see wins the queen.  Am I missing something?  Thanks for any help!

Something's wrong. Black's in check with white to move.

Yeah just wins the queen.

Sorry - made a mistake on the white queen placement - now corrected

Looks like a clear win for white. What's the starting position of the problem? Maybe I can look it up.

You can look up on chess mentor but the starting position has black king on h3, white knight on g4 and white queen on f5. All other pieces are unchanged from the position in my original post. White to move first.

Looks like 3...Kb4 is better.

I looked it up. Even if white can still win from here, the intended solution is faster.

Well spotted - we no nonger have the discovered attack on the queen - the analysis in Chess Mentor is clearly wrong - yours is better - thanks!

7.Qd2+ is an extremely tempting idea that often catches strong players. Black's reply 7...Kb5 is forced as 7...Ka3 and 7...Kb3 both allow mate in one via 8.Qb2. But 7.Qd2+ Kb5 8.Qe2+ appears to win the black queen. Both 8...Kb6 and 8...Ka5 run into 9.Nc4+ and again the queen on e7 falls (or 8...Kb4? 9.Nc2+). But there is a catch! Black plays 8...Nd3!!, vacating the c5-square for the king. After 9.Qxd3+ Kc5 there is no mate. And remember, the queen plus knight are insufficient winning material, so Black gets away! Cute, huh?