Oh, I was just reading the manual for silo. What I wrote was not entirely correct:
The program /sbin/silo is used to install the first stage loader by
copying the right first stage loader into the bootblock (unless the
correct first stage is already installed and the -f option is not used
to force it), writes the block number of the first block of the second
stage loader (usually /boot/second.b) into it and into the second stage
loader it records all the block numbers of second.b and the name and
location of the configuration file. The configuration file itself is
parsed by the boot loader at boot time. See silo.conf(5) for details.
This means that the /sbin/silo program must be run only if you install
a new version of SILO or if you move the second stage loader on the
disk. Unlike the LILO bootloader on the Intel platform, you don't have
to rerun it every time you make a change into /etc/silo.conf or when
you install new kernels.
[...] (if the second
stage loader is moved away or is crippled it might actually print less
letters from that string and die).
If you recently modified the layout of the disks, perhaps you need to just run 'silo' again to make sure that 'second.b' can be found?