Thanks to both of you for the replies, I really need to get to the bottom of this as it is spoiling my racing.
It is a powered 7 slot hub, it was only a cheap one off Ebay, but it has it's own power supply and should be 500mA per socket.
If there is an issue with the grounding, how would I fix that ?
I have moved the steering wheel back to the main PC case, and the Pro-Race and JC32 are still in the hub. In the last 24hrs, the Pro-Race display (& its buttons) has frozen 4 times - on three of those, it resumed operation after a few seconds; on the other occasion I had to unplug it, plug it back in, and restart SimDash. It then worked ok again.
The JC32 button box so far has had no problems.
I would begin to suspect a fault in the Pro-Race except that the steerng wheel has frozen a few times as well, so I am thinking it must be something to do with the USB.
I should add, that when it happens, there is never any slow down of the game, it continues running perfectly well, so I don't believe it is a memory problem. It feels more like USB or power block of some kind.
I have ordered a USB extension so that I can move all three devices to the main case as another test.
The only other solution so far was offered by Brian Clancy, and that would be to use a PCI USB expansion card, which I will certainly try if necessary, but if you can think of anything that would cause this momentary (sometimes terminal) freeze/bottleneck/ or whatever it is, then I'd be grateful.
Many thanks
Keith
