the important numbers in the permissions are the last three, they set the permissions level for "Owner, User, Everyone"
777 = Read, Write, Execute for all 3 user levels
775 = Read, Write, Execute For Owner and User. Read and Execute for everyone.
750 = Read, Write, Execute for Owner, Read, Execute for User, None for everyone.
640 = Read, Write for Owner. Read for User, None for everyone
the problem is the 640 and 750 permissions. the everyone user needs to have at least read permissions. 744 or 766 would do the trick.