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

sounds like you need to check the video output mode.. sounds like 50hz refresh rate instead of 60hz, or if you are running PAL then you need to be running 50hz instead of 60hz.. Try changing the resolution out on your Denon DVD player.
Thanks. I will give this a go.