Thanks for the good work. It helped me a lot. Two things I find out:

First, the save panel delivers url as nil in a sandbox. It looks like, that the sandbox does not like to initialize the directory url with a file path. You have to set the following:

if ([url isFileURL])
{
	homeURL = [url URLByDeletingLastPathComponent];
}

savePanel.directoryURL = homeURL;
savePanel.nameFieldStringValue = [url lastPathComponent];

and it will work now.

At at second, you have to set the storeType explicit to NSSQLiteStoreType, if you use SQLlite storage. This worked fine for me.