Here's what works for me:
Set the BIOS to boot sequence CDROM, C, A: (or any with CDROM first)
At pwr-up or reset, get your drive door open, and wait until the BIOS is polling the drives for type, size, etc. The controllers respond with "primary Maxtor, blah blah, secondary not present; secondary drive controller master PCRW804 or whatever, blah blah."
WHILE this polling takes place, shove the drive door closed (a gentle push won't hurt, but use the close button if possible.) Usually my disk-in light begins to flash once/sec immediately. _IF_ I get the timing right, the controller begins to handshake the cd drive to read the boot sector at just the right time to catch and read it. This is indicated by a continuation of the flashing disk-in. I've missed it if the light starts flashing dimly, and the BIOS starts to boot from C. Time to hit reset again...
I noticed this first with Knoppix 3.2 from last summer; never happens with the 3.1s I've got.
This tricks the drive/controller into reading the boot sectors without pre-positioning to where it THINKS the boot sector should be, and instead SEEKING it. I've found that after changing my boot sequence and booting from floppy or even another cd and then Knoppix it sometimes will boot right up; usually the first attempt of the day works, too. Annoying, yes, and the ugliest of solutions, but perseverence pays off.