Does LinuxMCE works with HDMI?
I also have DVI to HDMI to a 50" Sony TV. Max resolution I can get however is 720p. 1080i or p just gives black screen, but I read that it seems to be an nVidia driver issue.
It's more of a TV issue. My TV also required a special modeline to get it to work at 1080p. I had to do a lot of googling and tinkering to actually get it to work, but I eventually did.