SA Explorer 4250HDC - Poor HDMI output

I tried connecting the HDMI output from an SA Explorer 4250HDC (the "best" STB that TWC Raleigh provides) to my Hitachi 51GWX20B via an HDMI-to-DVI cable. The picture quality was so bad I had to use the component outputs instead, which give a perfectly fine picture. With the same HDMI-to-DVI cable I get a fine picture from my Panasonic DMR-ES46V DVD Player, so I don't think it's a cable problem.

Has anyone else had this problem? Any tricks I should know about the 4250HDC that might fix the problem?

Thanks,

tcpasley