When it does this do a <CTRL><ALT><F?>
where the ? is replaced by one of the function keys. I can't remember offhand, but one of the function keys will show what errors are being reported during the install.
Do this at the point that it locks up and see if it gives a clue as to what the problem is.
You can also enter in your own commands at <CTRL><ALT>F2> to see if it is really locked up (or only "mostly dead" ala "Princess Bride")
Kinda sorta sounding like a hardware problem with the disk tho...