Installing "Everything" causes SILO installation to fail. The error reported is "mount failed: device or resource busy". I checked and it was trying to mount procfs under /mnt/proc, but procfs was already mounted there, which explains the failure. So I by hand ran "umount /mnt/proc" in VC2's shell. Then I selected "RETRY" and the bootloader installation worked just fine. Choosing a more minimal installation makes this problem go away. This means that some packages postinstall process causes /mnt/proc to be mounted. My suggested fix is to force a "umount /mnt/proc" before SILO installation code runs in the installer, ignoring the error status. This will guarentee that the problem will not occur. I can test the fix for this here, just send me a new tftpboot install image for sparc64.
this seems fixed in the errrata install2.