Problem connecting from pgadmin: CACHE LOOKUP FOR USER XX FAILED

I created a database on a linux server and I configured it so that on
pg_hba.conf that the server wouldn't, validate passwords, but later I
changed the security to validate passwords. But after that, I haven't been
able to view table definitions or other tasks on pgadmin, except SQL Querys.
I can connect on ODBC connections an open and use the tables an databases.

What could I do?

Below is the log on PGADMIN.LOG.

Thank you for your help.

Ligia

Error Details
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Error Number: -2147467259
Error Description: Error while executing the query (non-fatal);
ERROR: cache lookup for userid 516 failed
Error Source: Microsoft OLE DB Provider for ODBC Drivers
Subroutine of Function: frmTables, cmdRefresh_Click

System Details
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Operating System: Windows 98 v4.10 Build 2222
Additional Info: A

Environment Details
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Application Path: C:\PROGRAM FILES\PGADMIN
Datasource: chequesdegerencia
Tracking: False
TrackVer: 0
Connect: Provider=MSDASQL.1;Extended
Properties="DSN=chequesdegerencia;DATABASE=chequesdegerencia;SERVER=s-inform
atica;PORT=5432;UID=lmpimentel;PWD=******;READONLY=0;PROTOCOL=6.4;FAKEOIDIND
EX=0;SHOWOIDCOLUMN=0;ROWVERSIONING=0;SHOWSYSTEMTABLES=0;CONNSETTINGS="
MDAC Version: 2.6
DBMS Version: 07.01.0003 PostgreSQL 7.0.3 on i686-pc-linux-gnu, compiled by
gcc egcs-2.91.66