In the admin if you move a group (e.g. change its parent) all of the links break to files and photos, incl group logo. The path format is relative /groupid/somenumber/name of file e.g. /4/40/paris.jpg and when you shift the group, to say group id 12, it rewrites the path as /12/40/paris.jpg BUT the image is still sitting in its original location - its just the database path that gets updated and the new folder made - the image doesn't get copied or moved. Suspect it might be a permissions issue - ability to make a new folder but not copy into it.