BUG #2300: Error in upper function

The following bug has been logged online:

Bug reference:      2300
Logged by:          Kashin Oleg
Email address:      kashin.oleg@mail.ru
PostgreSQL version: 8.1
Operating system:   Suse 9.1
Description:        Error in upper function
Details:

My database is with UTF8 encoding. When I use function "upper" for any filed
of table I get the next error
"Invalid multibyte character for locale".
Example:
select from users where upper(user_login) like '%';
I rewrote such SQL query like next one -
select from users where lower(user_login) like '%'; and everything now is
ok.
Thanks.