Hi there-
Had the same problem. Bought my 325 used from someone going to a 4-disk RAID setup, so I'm not sure which drives were in it before, but I bought the 3TB Hitachi drives based on reliability records, capacity, price, and the fact that they're listed here as tested and working with the 325. Installed the drives, tried to set up the NAS, and.....hangs at 58%. I think it said it was 58% done "Initializing", and did not even start to format the drives.
So: I tried updating to the latest firmware, but the setup still hung at 58 percent. Here's what eventually worked for me. Pop out one disk with the lever on the back of the unit, then set up the NAS with just one disk installed. That worked fine. Then I powered down, used the lever to pop out the formatted disk and popped in the other disk and set up the NAS with that disk installed. Each time, the DNS-325 had no problems initializing or formatting the single drive. Then I powered down again, inserted both disks, went to disk setup, specified RAID 1, and the NAS set things up properly.