My RT 660 started doing weird stuff a few weeks ago...occasionally Alvin and the Chipmunks got in there and would talk to you, the voice prompts would only work at the initial start of the route, and would sometimes interrupt as if it were making an attempt to give a voice prompt, but would interrupt and not say chit, but hold the radio as if it were still talking, and occasionally there was a high pitched squeal through the headset. So, for one thing I got the NIM replaced under warranty with the newest version (A, I think). Second, I sent the unit back to Garmin, and they sent me a replacement. Went for a ride today and all is well thus far. But I did notice one thing different: when giving a voice prompt now, it says the word "dot" at the end of the command. For example: Turn right in .5 miles. Dot. I have not heard this previously, so assume it might be some kind of firmware update?

My train of though is that perhaps the "dot" lets the NIM know, in no uncertain terms, that this particular voice prompt is done, so return to previously scheduled programming (XM, Ipod, FM, etc).
Has anyone else noticed this? It's working now, that's the main thing.