The procedures for using patchadd with the -C destination specifier to patch a miniroot on SPARC and x86 machines have changed. You must now unpack the miniroot, apply patches, then repack the miniroot.
See the following for the detailed steps:
Chapter 5, Installing From the Network With DVD Media (Tasks), in Solaris 10 10/08 Installation Guide: Network-Based Installations
Chapter 6, Installing From the Network With CD Media (Tasks), in Solaris 10 10/08 Installation Guide: Network-Based Installations
Chapter 7, Patching the Miniroot Image (Tasks), in Solaris 10 10/08 Installation Guide: Network-Based Installations