This happened to me, too. I have an N810, so it couldn't be something odd about an SD card. I suspect it was the rtcomm Internet Communications Software development update that did it, but I can't prove it. After reading the various discussions here, I decided to re-flash the device, *and* re-format the internal card. I did that via the control panel's option to clear the memory. That fixed it. I don't have the nerve to re-install the rtcomm update to really see if that is the culprit.

I'm glad I remembered to write down the license code for my upgraded Maps application! I also had to re-download the maps, which thankfully worked OK. Other than that, this procedure fixed the problem. In a way, it was refreshing to go through the exercise of wiping the device and starting over. Made me confident it could be done, and life goes on!