You set the partitions as ext3 in cfdisk? If you really did do that then you've discovered a new function of cfdisk.

You can set the swap partition type to 'swap' or 'type 82' simply by selecting [type] and hitting <enter> a few times. It will then be Linux swap. The other partition only need be type Linux which is default for cfdisk.

Now....I presume you know about dpms and the monitor blacking out to save power. Hit the up arrow when the screen goes black and see if it comes back. Don't hit <enter> or <space> as you may unknowingly select something.

Another something to try? Boot like so:
knoppix testcd

It should return 'Everything looks ok'

If none of the above works then my last suggestion is to try the text mode installer. Just boot like so:

knoppix 2