As nobody has replied to this yet, is there any additional information that you can give that may help?
If you are really saying that pressing the white TV button is causing your HDR to change channel, what happens if you press it again? does it do the same again?
Do you use the Humax remote to control your TV, and does this work OK?
Have you tried changing the remote control mode that your HDR uses, ( see
This Thread ) this may help with your problem.