mbox noisy
 

This is a followup request for help from yesterday.
Brand new mbox. Install went well, no crashes, LE works fine. MBOX however is very noisy on left headphone out (hiss, pops, whirring). This sounds like system noise that varies when the cursor moves or a window is open. The output is clean when the mix knob is turned to input. I installed cs9 thinking it was a SP2 issue but no help. Disabled other soundcards, network adapters - no help. My next option is to unistall SP2 and install SP1.
Anyone run into this kind of problem before?
Thanks, Bob

WIN XP Pro SP2
ASUS A7N8X motherboard (NDIVIA nForce chipset)
AMD Athlon 2500+ processor
1 gig RAM (Kingston)