Weird problem with new PC (Radeon 6870)

Hi all.

I built a HTPC yesterday with a Radeon 6870 and am experiencing a strange problem and was wondering if i could get some help?

The problem i'm seeing is, when i boot up my HTPC, which is connected to my Onkyo Amp via HDMI, the mouse cursor on Windows 7 is quite laggy and 'jittery', it just doesnt move smooth at all.

Now, here's the weird thing, when I then unplug the HDMI from Radeon, and then plug it back in, the cursor is then really smooth and as it should be. Which I thought was quite strange.

Obviously I do not want to have to unplug and then plug in everytime i boot the machine, does anyone have any ideas what this could be?

I'm completely new to Radeon cards so not sure if there's a setting somewhere in the Catylist Center which might fix this?

Any help would be mostly appreciated

Thanks for reading,

IdioTequE

Can you please describe the connections once again?

HD 6870 ----> (hdmi) --> TV?

OR

HD 6870 ----> (hdmi) ---> Onkyo ----> TV? I am not sure if you can even do this?

We need to know exactly how this setup is. Thanks