Reposting here to see if a different set of eyes and location might be able to give a better direction, thanks!
I have a Vizio hdtv and a sapphire HD5570, running windows 7 HTPC. I thought the card had an HDMI but i ordered the wrong version, and got one the has display port, dvi, and vga.
Anyway, here's the problem, I used to be able to get picture on the tv through a dvi to hdmi adapter. I've got hdmi plugged in tv port 2, and sometimes the screen was blank. a simple solution, I would switch to a different input, and then switch back worked fine.
later I updated the drivers and things worked great! it stayed on all the time, no problem and i could even see the boot up process on the tv (before i couldn't until i got to the log in screen). Then because I'm constantly tinkering, i was installing a usb device, told the device manager to scan for new hardware and my screen went blank, and wouldn't come back, even when I used a VGA cable that i had used originally (before getting the dvi/hdim adapter).
I hauled out an older monitor, that worked fine and I re-installed the drivers. dvi/hdmi worked again, as an extended desktop. So I set the dvi/hdmi tv to primary display. turned the computer off, unplugged the other monitor, started the computer up and nothing on the tv. I tried switching off the input and back again, nothing. I plugged the vga cable into the tv and got picture.
later I turned everything down, then turned the tv on, set it to the hdmi input and started the computer. I got picture at the log in screen again. My wife watched tv for a bit (switched the input) and when going back to the computer, no hdmi picture but the vga is working. Tried shutting it all down and starting up again, like last time, no hdimi, yes vga.
so currently, i get intermittent dvi/hdmi and it's not consistent so I can't figure it out. I do have the VGA working, and the weird thing here is that if i check into the screen resolution section of windows 7 or ccc, i see two vga displays listed, the tv and something else (i think a profile for the old monitor I dragged out). The default has my screen extended to this "ghost"display and I can roll my mouse off the side of the screen as if it were extended. I can't disable the ghost display either, nor do I have a second vga device plugged in.
its most likely a driver issue. they... act up. with HDMI sometimes. Anyway. uninstall it and go back to the previous working version. you probably grabbed the most recent when you reinstalled the first time, which makes perfect sense of course, but it seems to be causing you issues.