Re-creating the sup area /clean doesn't help, still the same error. It 
seems to be a problem with pkg_admin and a option provided in the makefile 
for the installation:

=> Fixing buildlink references in files-to-be-installed.
maiko# make install
===> *** No /usr/pkgsrc/distfiles/pkg-vulnerabilities file found,
===> *** skipping vulnerability checks. To fix, install
===> *** the pkgsrc/security/audit-packages package and run
===> *** '/usr/pkg/sbin/download-vulnerability-list'.
===> Installing for digest-20021220
===>  usage: pkg_admin [-V] command args ...
Where 'commands' and 'args' are:
 rebuild                     - rebuild pkgdb from +CONTENTS files
 check [pkg ...]             - check md5 checksum of installed files
 lsall /path/to/pkgpattern   - list all pkgs matching the pattern
 lsbest /path/to/pkgpattern  - list pkgs matching the pattern best
 dump                        - dump database
 pmatch pattern pkg          - returns true if pkg matches pattern, 
otherwise false is already installed - perhaps an older version?
*** If so, you may use either of:
***  - "pkg_delete usage: pkg_admin [-V] command args ...
Where 'commands' and 'args' are:
 rebuild                     - rebuild pkgdb from +CONTENTS files
 check [pkg ...]             - check md5 checksum of installed files
 lsall /path/to/pkgpattern   - list all pkgs matching the pattern
 lsbest /path/to/pkgpattern  - list pkgs matching the pattern best
 dump                        - dump database
 pmatch pattern pkg          - returns true if pkg matches pattern, 
otherwise false" and "make reinstall" to upgrade properly
***  - "make update" to rebuild the package and all of its dependencies
***  - "make replace" to replace only the package without re-linking
***    dependencies, risking various problems.
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/pkgtools/digest
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/pkgtools/digest
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/pkgtools/digest
maiko#