Trouble with the Arduino and 'PING' Ultrasonic Sensor

I would really appreciate it if someone could help me with this.
I have connected my Arduino to my computer... I set the ports and everything and tested it with the 'Blink' program... everything was fine... then I connected the 'PING' ultrasonic sensor to the Arduino (as shown in the PING tutorial) - a message flashed on my computer screen saying that the USB device was pulling too much power and thus, has been disabled, in order to protect the computer! ... so I connected the Arduino to a DC adapter, hoping this would help... but nothing...
PLease advice on what I could do to fix this! Thank you!

could try #2 in arduino servo walk through from here: http://rcarduino.blogspot.com/2012/04/servo-problems-with-arduino-part-1.html