Hello! i have a problem, when logic power on Dagu is NOT powered from Arduino, motors rotate easily in both directions, but when i connect logic power (5V) from Arduino, motors begin to rotate harder in one particular direction. Firstly i connected logic from 5V Arduino pin which is near analog pins, then i tried to connect from ICSP pins, same result. Then I've done everything exactly like you to exclude my mistakes, but it doesn't work.
P.S. Moreover i bought two Arduinos and two Dagus, I thought i fired smth, but motors bahaves on both.
P.P.S Everything works fine with Pololu motor driver shield and Arduino - motors rotate easily in both directons.