When I record audio I get a regular clicking or pulsing noise on playback.  I estimate the frequency of the clicks to be about 10/second.  The noise shows up with playback on on both speakers and headphones.
 
Hardware & software are: 
    Quad-Capture
    Shure Condenser Mic - phanto power on
    Dell desktop computer w/Windows 7
    Sonar X2 Essential
 
What I've tried:
    Running a ground wire from the Quad-Capture to the conputer power supply
    Switching USB ports
    Grounding Lift settings - both normal and lift
 
Any help would be appreciated!

Do you get the noise only during recording ?

How about when not recording ? - on the Quad Capture, turn the MIX knob fully to Input and check if you hear any noise with the mic input connected ?

Thanks Albert.  I did the test you suggested and I'm not getting any pulse noise -- just hiss if I turn the volume all the way up.

I get a loud pulsing noise when recording any vocal track! Just started out of the blue. Does not pulse when playing back any audio from Sonar or anywhere else.