I've started to recreate the drive with the files mtrok2 has provided (although I believe these are the same ones I was already using)
I just noticed one difference in my partitions and the ones you showed and mentioned, mtrok2. I do not have an unknown sdc5 partition.
Could this be the cause of my problem? If so, how can I solve this?
The unknown sdc5 is the Linux swap partition. I do not think it is the problem, but if you want you can try to write the swap image to it which will turn it black and unknown. Yeah the images I uploaded is the same as the one you were using, but I know this one is working. Your problem is either with sdc6, the mbr or the board, but I will exclude the MBR since you are able to boot from USB. You can try LacieHasser method http://forum.nas-central.org/viewtopic.php?f=141&t=361&start=15
. I used it before and it will make your disk network work but without the usb function. At least if you try his method and you get it working than we will know that's the problem is not with the board.