I don't know why the program is failing to write a BluRay -- but if it's able to create a DVD, then you're in good shape, software-wise. You don't when you've last run Disk Cleanup and Disc Defragmenter, but if you've got 3.8 terrabytes of data on 4 terrabyte drive, you may well have fragmented files that are keeping larger processes (like BluRay production) from working. Complicated RAID setups can also work against you -- but that's just what I've heard. I'm no expert there.
But FWIW, I still think a BluRay of your standard def video files is overkill. Your original video is still only 720x480, regardless of whether your burn it as a 720x480 DVD or blow it out to a 1920x1080 over-rezzed video. But I guess that's your choice.
I'm sorry we can't offer more direction. You've clearly got a powerful enough system to do this kind of thing without working up a sweat. But there's something going on that's just not obvious, based on the information you've given.