I have had my 276C for quite a while now and love it because of the easy to read screen in bright sunshine and the fact that I can use it on my boat to navigate. I finally had my first problem.
One day, I wanted to find a street address and the menu item "Address" was not there.
Finally the third call to Garmin tech support resolved the issue. Previous techs had me doing all kinds of stupid things; but since I had worked on the problem for a week and had not solved it, I was willing to do what I was told. I won't bore you with the details; only the solution.
It seems my card had somehow become corrupted. I inserted a different card, downloaded the newest edition of Mapsource, highlighted the maps I wanted in the device, transferred over the East coast and all was well.
I hope this helps anyone else who runs into this situation.