Help - Colour C-Touch - No C-Bus connection

I have a client who has a Colour C-Touch that, following a power failure, will no longer connect to C-Bus. The screen displays the no c-bus icon with an error message saying it cant connect to C-Bus as the Com port (3) is in use by another device.

Apart from that, the screen works perfectly, I have succesfully uploaded the latest firmware, Home Gate and a complete new project via the Ethernet port. I know C-Bus is present at the touch screen as if you replace it with another c-bus device (ie Bus Coupler) then scan the network, then the new device appears, and C-Bus voltage levels, burden and other usual checks come out good.

I think this error is down in the Windows layer, and that the comm port settings need changing to reflect the port that the C-Bus firmware is trying to connect through.

I would have thought that there must be a way of getting into the Windows software and reconfiguring the com ports. I guess that this would involve accessing the windows Registry (HKey_Local_Machine) and I understand the risks in doing this, but given that a new touch screen is ?2.5K sterling and it doesn't currently work any way, I figure I've got nothing to lose.

So has any one else experience this problem? and managed to fix it?

Thanks in advance

Paul.