Satellite tuner is not recognised by Windows 7 64bit WMC

I am tearing my hair out here, so i am hoping that someone here can help me solve this mystery.

I am running Windows 7 Home Premium 64 bit and using a TechnoTrend TT-connect S2-3650 (UK). The TT connect works fine using DVB viewer (so I know that the drivers work and that the tuner is on the correct satellite). It also works fine on WMC on my Windows 7 Professional 32 bit media centre PC - it finds all the channels, including BBC1 HD .

However, when I try to setup the tuner on my main PC, WMC finds the tuner, but states that no signal is being received. The light changes from green to red when WMC searches for tuners, indicating that for some reason WMC is preventing the TT connect from accessing the satellite signal.

I have tried everything, including stopping the WMC processes, and deleting the contents of the ehome folder (ProgramData\Microsoft\ehome) and running setup again.

So, can anyone help explain why the receiver works perfectly using other applications - and also perfectly in another windows 7 media centre PC in WMC - but not using WMC in my main PC?

 

Anybody?