Flickering when playing DVDs on Denon 2910

I have a Denon 2910 connected to Pioneer Plasma 504 using HDMI to HDMI. I noticed flickering on all DVDs that I play. The flickering is less when I turn off the Pure Cinema mode on the Pioneer. The flickering stops when I change to component video connection. Is the flickering due to the HDMI cable as told by my dealer who sold me both the Plasma TV and the 2910? I have a 3 meter run and the HDMI is locally made in Singapore. Should I change the cable? If yes which HDMI cable should I buy? I still need 3m

Thanks for your advise

Jonathan