USB3 problems with Ubuntu 14.04 LTS and Gigabyte 990FXA-UD3

Hello to everyone on this list, I am hoping someone here will be able to 
help me figure out why I cannot get USB3 running on my new PC.

As you may have gathered from the message heading, I have installed 
Ubuntu 14.04 on a PC I just put together, based on a Gigabyte 990FXA-UD3 
motherboard.

Initially I had a problem with the IOMMU settings breaking networking 
and USB completely, but after googling a bit, I sorted that out.

(see here: http://ubuntuforums.org/showthread.php?t=2261468)

However, even though I now have this PC online, I still don't have USB3 
or automount-and-open-nautilus-working.

I have posted about this on the Ubuntu forums, but have not received any 
solutions yet.

(see here: http://ubuntuforums.org/showthread.php?t=2264889 and here: 
http://ubuntuforums.org/showthread.php?t=2266149)

Can anyone tell me what I am doing wrong?

Cheers,

Brad Wilkinson
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