Strange behavings with a USB3/USB2 hub

My questions seems to span a couple of sections but , since it concerns external HDDs, I am putting it here  

I have a 10 port USB hub. There are 4 USB3.0 ports and 6 USB2.0 ports. The hub is plugged into a USB3.0 port on the back of my computer. The hub has external power but doesn't seem to need it so I disconnected the power as the devices (external HDDs) I plug in all have their own power. The behaviour is the same with or without the hub being powered.

I have 4 USB3.0 Seagate Expansion external HDDs plugged into the 4 USB3.0 ports and they worked perfectly for weeks.

One day, when I switched on, I got 4 Windows warnings "Device can perform faster on a USB3.0 port". I had changed nothing.... Now Windows was seeing the 4 USB3.0 ports as USB2.0  

Very occassionally there would be NO warnings but now I ALWAYS get warnings.

I tried for months to get support from the manufacturer - mbeat but there wasn't a response to my 4 or 5 requests for an explanation and/or support. I have since found that mbeat don't support their products  

I've tried Windows 7 forums but got no responses  

In desperation I bought another 4 port USB3.0 hub and transfered the 4 USB3.0 external HDDs to it. Lovely, NO warnings from Windows 7, 64bit on switch on. I thought my problem was solved  

Next day 4 warnings!!!!  

I tried splitting the load.... 2 USB3.0 external HDDs on each hub - 4 warnings  

Has anybody had this problem and solved it?  

Can anyone provide a solution as I'm desperate    

My motherboard is a GA-P55A-UD7 and CPU i7 with 8Gb memory running Windows 7 64bit if it is any help?