postgres solaris 2.6 error message

I'm getting this error when trying to run postgres under solaris 2.6 and
posgrsql 6.5.1.

postgres@vizard:~/postgresql-6.5.1$ /opt/pgsql/bin/postmaster -i -S -p5432
-D/opt/pgsql/data
IpcMemoryCreate: shmget failed (Invalid argument) key=5432001,
size=1073152, permission=600
FATAL 1:  ShmemCreate: cannot create region

Any ideas?

David