A common cause of this problem is that the floppy drive may be of the newer ATAPI type common to newer laptops especially, as constrasted to the older /dev/fd0 floppy type. The install kernels come with ide-floppy support needed for ATAPI compiled in, but the kernel installed has ide-floppy service through a ide-floppy module.
There are three workarounds. 1) During your 2nd install boot, use the original install disk with "rescue root=/dev/hd(your linux partition)". Read the documentation on your rescue disk. 2) After you've completed an install, compile a kernel from source with ide-floppy compiled into the kernel, as opposed to a module. Copy this kernel to /boot/vmlinuz, and run "mkboot", which expects a /boot/vmlinuz to make a new bootdisk specific for that partition. 3) install the mkrboot-????.deb package, which will provide you with numerous other options for boot disk making. MarvS