Please Help with filtering LM4752TS

[kriswalsh]

I am using a National LM4752TS Amplifier and I am using the suggested schematic as shown on Page 7 of the National Spec.

http://www.national.com/ds/LM/LM4752.pdf

I am also using the suggested Values for Components. I have also followed the PCB layout as suggested in the same spec sheet.
The amplifier works beautifully when powered with a 12VDC PS and a clean input source, in this case and Ipod) is used to play music. When there is no sound coming for the soundtrack the amp is basically silent. When playing content from the Ipod the sound is quite good. However, when I use a PC as the sound input source, the amp makes all kinds of bizarre noises from crackling, to whining at a high to low pitch frequency. The Amp also produces some weird noises which occur in conjunction with the mouse moving around on the screen or clicking on icons on the screen.

Any help with filtering this noise away would be greatly appreciated. I have tired grounding the chassis of the PC, which seems to help somewhat, but does not eliminate the problem enough to be considered satisfactory.

Thanks for your time!