Motorola W755
Memory chips
Take the same card and read it from a computer and it shows the full 8GB so the phone is not formatting the chip down to 4GB, but the phone just doesn't recogzine the extra space.
Some day when I'm bored, I'll use the computer to fill up the first 4GB of the 8GB card and see how much free space the phone thinks it has left.
The problem MAY be that the phone cannot access more than 4GB, or it MIGHT just be that the routine that displays the used and free space only counts to 4GB.