problems logging in through phpPgAdmin

We are using phpPgAdmin 4.2.3 on Redhat Linux 5 to access local postgres 8.4 databases and some remote postgres 8.0 and 7.4 databases. If I set the pg_hba.conf settings to "trust" I can login to phpPgAdmin with any password at all or with no password at all. If I change the "trust" to "md5" I get "Login Failed" errors on every login (we always login as postgres), even though the password is correct. When this happens I check the log in pg_log folder, and all it says is "FATAL: password authentication failed for user "postgres"". In the phpPgAdmin config.inc.php file, we have this setting:
$conf['extra_login_security'] = false;
We are not having any problems logging into the databases from the command line.
Thanks in advance for any suggestions.
Julie

julie(dot)davenport(at)ctcd(dot)edu