HD44780 based LCD display shows half-black, half-blank
The problem with the display not initializing was because of a loose wire. It was either RS or RW, that was left floating.

My logic analyzer showed it being in the low state, but seems the LCD's controller thought otherwise. (Different kind of input)

A tip:
Check your wirings: not connected != input driven low

A logic probe, which emits a high, or low pitch sound depending on the signal, helped me find the problem. It did not give any kind of sound at all on that pin.