Bootcamp Broken on Mac Pro 5,1

[DJC631]

I'm running a 2012 Mac Pro with an internal SSD. It was partitioned with a Windows 7 installation via boot camp and was running fine. However, a few days ago I went to change the startup disk and received: "You can’t change the startup disk to the selected disk. The bless tool was unable to set the current boot disk."
Went to reset my partition on the SSD and Bootcamp Assistant tells me the Mac doesn't support Bootcamp.

I'm at a loss, any advice?

 

[DearthnVader]

hmmmm............

Have you tried to reboot holding the option key and select the Windows partition that way?

Do you have more than 4 partitions on your SSD?

/Applications/Utilities/Terminal.app

diskutil list

 

[DJC631]

I'm using a GTX graphics card, so I can't use the option button at startup. I tried to use my original graphics card, but I have no video for some reason. So for now, I have no reliable way to reinstall stuff.
No, the SSD had only 2, 3 if you count the recovery partition.

 

[DearthnVader]

I'm using a GTX graphics card, so I can't use the option button at startup. I tried to use my original graphics card, but I have no video for some reason. So for now, I have no reliable way to reinstall stuff.
No, the SSD had only 2, 3 if you count the recovery partition.

What about the EFI partition?

I also have a Microsoft Reserved partition in addition to the Microsoft Basic Data partition, but I have Windows 8.1.

If you have a hybrid gpt mbr partition table, you can't have more than 4 partitions, you'll have to convert the disk to pure GPT. There is a nondestructive way of doing it, but I'll have to see if I can find it again. I had to do it for my disk as I have 14 partitions.

I don't know why it would stop working for you tho( booting Windows ), unless you added a partition sense the last time you booted Windows?

 

[DJC631]

What about the EFI partition?

I also have a Microsoft Reserved partition in addition to the Microsoft Basic Data partition, but I have Windows 8.1.

If you have a hybrid gpt mbr partition table, you can't have more than 4 partitions, you'll have to convert the disk to pure GPT. There is a nondestructive way of doing it, but I'll have to see if I can find it again. I had to do it for my disk as I have 14 partitions.

I don't know why it would stop working for you tho( booting Windows ), unless you added a partition sense the last time you booted Windows?

The whole Mac has stopped booting, so I think I've got more serious problems now, sadly.