I don't know what error you're referring, but whatever it is, it only affects the HVR-900, but not the PVR-350; so it doesn't look like DirectX could be the problem (because the same DirectX engine is used for both tuners, isn't it?).
I posted the error here,
you can also find it in your mediaportal\log directory, filename =error.log.
I agree with you, the error only affects HVR-900, so directx should not be related, but it's the only error I can find in our logs and it happens immediately after resume from hibernation.
In my country there are also some radio transmitting in DVB-T, so I had the idea to rerun the test using myradio.
I followed these steps:
1 switch on the computer
2 enter in mediaportal and remain in the main menu.
3 put the computer in standby
4 exit from stanby, mediaportal appear correctly in main menu
5 enter in myradio and tune one of the DVB-T radio channel
If igalan can confirm it we can exclude a bug in the TV module and think to something related to the driver management.