In the version of Gaia that went live today (5.31), we fixed the issue with maps being subject to random deletion in iOS5. Please see my last blog post for a recap of that little fiasco.
All users using iOS5 should update to v5.31 to avoid any issues, and if your disk is half full for any reason, you should also probably check your maps to make sure you aren’t missing tiles.
We apologize for any issues, and we’re back to work on new features and improvements. We should have route-making and satellite maps live in the next week or so!