I think the dimensions shown are "pixels" (3917056 or 4Mp as near as dammit).
You say "used to be able" so something has changed. Look at the output properties of the program you are using to print and/or printer properties. Also, what is the size of the printed portion? What I mean is, printing edge to edge on 6x4 will give only a 6x4 print. May sound obvious, but if for example a piece of photo paper slightly larger than 6x4 is used it will not print edge to edge - only 6x4.