Problem with 7.4.5 and webmin 1.8 in grant function

I newly installed the postgresql 7.4.5 and FC 3 in my server and transfer the
data from 7.3.2 with just a few problems. After I use the webmin 1.8 to config
the grant previllage to the users ,I found that there is an error in the grant
previlege .
postgresql --> Grant Previlege --> error

select relname, relacl from pg_class where (relkind = 'r' OR relkind = 'S') and
relname !~ '^pg_' order by relname : Unknown DBI error

What is the cause of this error and how could I handle this order?
Please make any comment, Thanks.
Amrit , Thailand