The iPodlounge is reporting a static problem with Appleis new 4th generation iPods. According to the site, the problem involves static through the headphone jack during certain hard drive operations. From the iPodlounge:
In extended testing of Appleis new fourth-generation iPods, iPodlounge has discovered and reported to Apple an apparent manufacturing defect affecting the headphone jacks of certain new iPod hardware. The defect manifests as audible static and noise interference in the earphones that is most prominent whenever a new iPodis hard disk is accessed. Similar interference was not detectable through line out (Dock Connector) output.
The iPodlounge says that Apple is looking into the problem; there is more information in the full article.