We havent pinned it down yet people but I believe by default Hardy tries to use a 800x600 75hz setting for video. I also have had this issue and it mainly affects ppl with a LCD screen. For those that do not know LCD's generally like 50-60hz on refresh rates, anything higher and you get the black screen, garbage on screen or a overscan msg on your monitors. Most LCD's will support a range of resolutions depending on make and size but they always have a NATIVE resolution, The one that there made for and will look the best by far.
I found for me when I install I have to get to the menu hit F6 and add a noacpi on the end of the Kernal modifier line. I then boot using recovery (second choice) and sometimes I also have to use the F4 option and select a generic monitor and VGA card and set the Resolution etc. Then once I'm in desktop ( I might add it took me 5 trys one time to find ones that worked ) I can use Envy in 1.7 or EnvyNG on the 1.8 and install the video drivers. Once I VERIFY they are set and the default I can then reboot and go about life without a hitch. ANYTIME YOU MODIFY THE KERNAL you generally have to reinstall them. One last thing I am just guessing at the default resolution and refresh but I have seen a TON of post on this. I hope this helps and if any Admins or Mods care to edit this post with better details feel free too. I am just posting what has worked for me and a few others I have helped.