Sound distortion at high frequencies on iPod photos?

There have been reported audio quality issues with the iPod photo since the end of last year (essentially, audible static and intereference when the iPod's hard drive spins up), but here's a different twist: some users are reporting some across the board sound distortion problems when listened to high-pitched tones not surrounded by other music. This apparently shows up quite clearly when listening to solo piano, and seems to disappear when using the line-out connection from the dock, prompting some to speculate the issue as being with the analog audio circuits driving the headphone jack. Is anyone else experiencing this problem?