Help with strange HU-650 behavior

Quick background - bought a 2006 S60 in January of 2008. Until last week, plenty of problems with the car, but none with the stereo (HU-650). Back in January 2009, I had a local car audio shop install the USA Spec iPod adapter in the car. Everything seemed fine.

Last week, something strange started happening. The stereo spontaneously starts changing bands with no input from me. For instance, when I am using the iPod (through the CD Changer), it will flip to one of the FM or AM bands. When I am listening to FM1, it will start flipping through FM2, FM3, AM1, etc. In other words, it doesn't just happen when the iPod adapter is in use, it happens no matter what I'm listening to.

Sometimes it changes bands once, and I'm able to just change it back. However, sometimes it just starts "freaking out," rapidly scrolling through the bands. This behavior seems like some sort of loose connection somewhere, I suppose, but I have basically no car audio expertise (thus why I wimped out and had a shop install the iPod adapter).

First question is whether anyone has an idea what this could be. Second question is whether it was likely caused by something the car audio place did. I'm not sure what to do - I figure if I take it to the car audio place, they'll say it's not their problem (they didn't seem thrilled with the adapter I brought in and asked them to install), or if I take it to the dealer they'll point at the iPod adapter and say it's not their problem, either.

Any help would be appreciated, thanks!