Half of R9 295 x2 Stopped working?

[Russell Smith]

Hi,
I'm hoping someone can help with a small issue I've run into...

I have a H81 Pro BTC Motherboard, and had a single Radeon r9 295 x2 plugged into it.

I was happily mining with Minergate, using the windows GUI. It has two sliders where you can allocate the % of GPU you're assigning to mining, and as the 295 has two cores, you get two sliders.

Recently I've added a Radeon 580, via a riser. That is plugged in and working, and in Minergate appears to be fine.

Now with that card added, I (obviously) have three sliders.

However, with the 295 and 580 plugged in, I have the issue that one of the 295's sliders is greyed out. Even if I drag it to 100% and it goes green, that half doesn't start mining or doing anything...

I've since unplugged the USB from the riser of the 580, to disconnect it, and then both halves of the 295 started up again, just like before I added the 580...

Any ideas why adding the 580 disables half of the 295 and what can I do to get all three working at the same time?

Any help really would be appreciated!

Cheers
Russ