Remote, but unshared filesystems, such as /, /var, /var/adm, etc. should be mounted with the llock option. Solaris 2.x does this automatically for remote /, but not for remote /var or /var/adm. If you don't specify llock, the system will hang when it tries to do stuff to the *[wu]tmp files, early in the boot process. And lpsched may fail if it can't lock /var/spool/lp/SCHEDLOCK.
Workaround: Add the (undocumented) llock option to the mount options for /var and/or /var/adm. (It should be fixed in /etc/rcS.d/S70buildmnttab.sh)