ERROR: Could not convert UTF-8 to ISO8859-1

Hello,

my database encodes data as utf8. The data I want to select contains
characters like äöü.

If I select some columns and change the encoding to latin1, then I get
the following error message:

select created, keywords from requests;
ERROR:  Could not convert UTF-8 to ISO8859-1

If I set the client encoding to utf8 by entering "\encoding utf8",
then the same select will print all the columns bu display

Ì for ü
ö for ö

and mess up other "special characters". The version of my postgres
installation is 7.2.1 on woody/debian.

Why does postgresql issue the error message "ERROR:  Could not convert
UTF-8 to ISO8859-1", when I execute a select statement after I changed
the client encoding to latin1 ???

fritz