I'm using this motor, made by adafruit: http://www.adafruit.com/products/168
The winding resistance is 72 W /Ø for our model. One thing I thought of is that the motor is rated at 0.3-0.4 amps per phase, so maybe I should multiply the expected current draw by 2, since the motor has 2 coils to energize (2 phases). Is this a correct thought process?
72 what? Ah, I see the datasheet - the problem is there are 4 different motors in that table, unipolar and bipolar, 12V and 5V. Have you _measured_ the resistance of the windings?
If they genuinely are 72 ohm then the H-bridge is misbehaving, but I think its much more likely you have a 5V 12ohm motor.
Yes if you use full-wave drive then two windings are on at once.