Whenever I've used knoppix, I sometimes get multiple I/O error's when it's booting. I just let it get on with it, and see what happens when it settles down.
Don't forget, it's a liveCD, this often means that any data bottlenecks are magnified as the whole distro is running from the disc, so would be much slower than if you had it running from a hard drive.
Does it manage to run, albeit slowly ?
Maybe you could give some system spec's so people can have a look to see if there's any other reason that it might run slowly.
Or perhap's did you download and burn the disc yourself? did you check the md5sum of the download to confirm it's integrity before burning it to disc?
There's many reason's that it maybe running slowly and giving you the error's. Also it would depend on whether you can get the net connection running while you are using it i.e. maybe that you've got dial up, so it's difficult to config with a hard drive installation, let alone get knoppix to use a winmodem.
These kind of snag's make it hard to try and help you diagnose the problem.
Maybe this helps/points you in the right direction?