Kento-
Remove the switcher from the chain just to troubleshoot the problem. If you have the HD DVD player connected directly to the Onkyo and have that conencted directly to the TV and have no problems then it's the switcher. I recommed one from
http://www.radiient.com/ The head of the company is Jano Banks, who is the #2 name on the HDMI patent. All his products actually work and fully meet the HDMI standards.