This has been an issue since Christmas for me. But when I start the game my default resource pack does not load automatically. I always have to go into the settings menu and return to the main menu to invoke "Loading Resource Packs. I dont need to do anything in the settings menu just enter and leave.
I use the City pack, but I have tried with DB Craft and others and its the same for all of them. None will load without a trip through the settings screen.