not sure why my dns-321 would not budge calling these drives anything other than 500GB. my hdd model is ST31500341AS and yes the firmware is upgraded to 1A (from 18).
I tried forcing 1500 in the format raid1 box by javascript overide via Opera (as some other guy suggested) but after the device come back on, the capacity is 500GB!
so, questions for you.
-Are you using raid-1?
-what is your hdd model #?
-what is your dns321 h/w version?