I have a 1-year old HRX and it does the same thing (sometimes stalls when engaging the blade). I've discovered a few tricks to avoid the problem:
(a) Make sure the engine is fully warmed up. Give it a good two minutes even on a warm day to get fully up to temp.
(b) Don't engage the blades on uncut grass. Especially critical if you have the mowing height set to a lower position.
(c) Press down on the handlebars slightly to raise the front of the mower deck when engaging the blades. Once up to speed, lower the deck slowly.
All that said, it is possible the throttle lever, throttle cable or governor are out of spec. You'd need a tachometer to confirm the engine speed (blades engaged, throttle to FAST) is 2,950~3,100 rpm. This is checked at the factory on every unit, so it's unlikely to be the problem. -Robert@Honda
Caveat: I work for Honda, but the preceding was my opinion alone.