DGR33

I have a Panasonic TH-42PX600U with Time Warner Cable. My DVR box is a Scientific Atlanta 8300 HDC connected via HDMI. When I switch channels there is a delay of up to 5 seconds between channels. I've switched out the box several times and I've had Time Warner at my house about six times with zero results. The last cable guy that was here claims the delay is because it has to switch between 480i to 1080i. When I used componant cabling the problem goes away.
I really want to use HDMI and now Time Warner says they do not support HDMI and the HDMI connection in the Cable box is strictly for convenience only for it's subscribers.
Anyone have any advice on how to possibly fix this? Thanks