Warning: long post
The other day we started off with a CityXplorer San Francisco 2011.40 loaded on the 1490's SD card and CN USA & Canada 2011.31 on the Nuvi's flash. And the most recent firmware, v5.10

After having arrived at our destination I switched to Pedestrian Mode (P.M.) and we continued on foot. PM functioned as it should have. Having reached our walking destination I switched off the GPS. When we returned to the car later, I switched the GPS back on (forgetting that it was switched off earlier while in PM) and told it to take us "Home". A few minutes later I realized that the device was still set to PM so I stopped the car and switched it back to Automobile Mode but I realized that from that point on the device was navigating in a strange way. I switched to the main menu screen so that I could cancel the current navigation request (i.e. Home) by pressing the X on the bottom left. However the X was non responsive. It was stuck there and wouldn't cancel and wouldn't go away, no matter how I tried.

Eventually I ejected the card which had the CityXplorer map on it and immediately the X disappeared and the device returned to normal. Now, I wonder if the moral of the story is that it's best to have CityXplorer maps on an external SD rather than on the main flash memory. If the latter was the case, I probably would not have been able to reset the device so easily without doing a hard reset or similar…