This is my first encounter of such a problem....At this point I want to look at the disk layout, see how it is formated; And another point I do not know if it applies, But I am aware of some issues that have been caused by the boot loader being located to far out of bios's range.
To look at the disk; from the install cd in "try ubuntu" mode, ctl+alt+t activates a terminal, post the output of these terminal commands:
<those are lower case "L"s>
sudo fdisk -lu
sudo parted -l
see what tale is told ==> BDQ