You can try: 'knoppix 2' and see if you can sucessfully boot into text only mode.

If you can successfully do this, then type 'dmesg |more'

You can read through this and see if you see any error messages.

My suspicion however is that you have a bad .iso image.

You can try downloading the md5 file to check out the file size.

You may need to download a new iso (sigh).