can't run on TCP/IP ports

When I attempt to run postmaster on a TCP/IP socket, I get the following
error:

FATAL: StreamServerPort: bind() failed: Permission denied
Is another postmaster already running on that port?
If not, remove socket node (/var/run/postgresql/.s.PGSQL.5432)
and retry.
/usr/lib/postgresql/bin/postmaster: cannot create UNIX stream port

There is no other postmaster running, there is nothing in
/var/run/postgresql, nothing else is on port 5432(switching to another
port doesn't make a difference), I am logged on as user postgres, the
user postgres owns all files in the postgres home directory, and
postmaster works fine with UNIX domain sockets. Does anyone have any
other ideas what could be wrong? I am running Debian 2.2