Radio Problem in my '06 XE

I have the 6-disc non RF factory radio. I was listening to an "AM" talk show yesterday on 1310 and my radio began to switch back and forth between 1300, 1310 and 1320. When it switches it only does so for about 1 or 2 seconds before going back to 1310. I thought it was a temporary glitch, but it was doing it again this morning. Anybody have any ideas as to why this is happening? Thanks.