I discovered one of my Jalapenos was running hot. Too hot to touch.
Here's what I found inside:
It looks like the fan somehow hit the heatsink, as you can see a couple of bent fins.
I have no idea how this happened. The unit used to blow air just fine, it didn't make any strange noises while I was around and I haven't dropped it or moved it about - so perhaps it happened during assembly - but the broken blade only just now moved around and jammed up the fan... or maybe the heatsink and fan just moved closer together due to thermal expansion(?)
Keep an eye on your rig temperatures people!