I have a pair of very healthy Bhut Jolokia (ghost chile) plants that I started from seed. They are very prolific bloomers, but never has yet set any fruit, despite being in full sun the entire Phoenix summer.

I have a couple of Scotch Bonnets growing right next to them that have given me loads of fruit, and still setting fruit even with the cooler days and nights.

Soil pH is about 6.5, have added magnesium and phosphorous. Fertilized with blood meal and bone meal once or twice.

What would cause one type of pepper plant to set fruit and another not?

If your Bhut Jolokia has flowers but no chilies, they may not be pollinated. Try using a small paint brush or q-tip to gently wipe pollen from one flower and then transfer it to another.

Actually, I forgot to mention that...I've tried hand pollinating with a q-tip. I've sat on the ground next to them several times and done that.

I sing to them, I beg them, I bribe them with promises of great salsa. Nothing.

They also have a very long growing period, up to 160 days before harvest. When did you start the seed?

High nitrogen can also prevent fruit set. Or low P and K.

I have been told that pollen usually ripens between noon and 3 PM every day.

And I agree with Dave, high nitrogen makes a beautiful lush green and usually fruitless plant.