ident client authentication

I have a problem with ident client authentication.
My server is debian sarge, pg version is 7.4.7, apache 2.0.54, mod_python 2.3. A python script is placed on the server and runs under mod_python in apache.

I make a request from firefox on a win 2k box to this server.
If I have
local  all  jim  trust
in my pg_hba.conf file, all is well, my python script runs and delivers the expected output.

However, if i have
local all jim ident sameuser
I get  FATAL: IDENT authentication failed for user jim, via mod-python debug and in postgres log.

jim is both a unix user (linux) and a postgres user.

Is this what would be expected?
How can I make ident authentication work?

Any help would be appreciated, including where this message should be posted if this list is inappropriate.

Paul Hide