I had a similar problem with my PII. My solution, though not eloquent, was to use 2.0 boot, driver and base disks to start the installation. I then had to upgrade one of the libs before I could then use dselect to install from my 2.1 CD's. dselect will tell you which lib needs updating. You then can copy the required .deb file to /tmp and use dpkg -i libxx.xx.deb to install the new lib. There is probably a better way around this, but this worked for me. It seems the boot kernel for debian 2.1 is more touchy about SCSI that the boot kernel for 2.0. I have even compiled new kernels based on 2.2.9 with no other problems with my SCSI hardware. I'm still new to linux, but I like to offer what help I can to return the favours of all the people on this and other lists that have helped me get this far.
Cheers, John Gay