Garageband freezes on opening file, says: "updating to new song format.."

Garageband freezes on opening file, says: "updating to new song format.." but cannot get further. Application is still running and can still quit normally or open a different file or do anything else you could normally do without an actual file open. 1 or 2 small files will open normally but the others will not. Any ideas on how to get out of this. very annoying as I have spend hours on a particular file and been saving work regularly.