I've been playing the awesome Harmonix rhythm game Frequency without incident for the last couple years and just recently a weird problem has come up. On the Fear Factory song (cleverly titled Frequency), both of the guitar tracks are heavily muted to the point that they can't be heard at all.
I've tried different surround sound settings on my receiver, and can't find any game options or PS2 settings that would cause this on that one song. And I can't see any scratches on the disc.