Invalid Unicode Character Sequence found

Hi All,

One very strange problem within the PostgreSql database.

When you issue the following command:

select id, title from docs where title like 'z%'; or
select id, title from docs where title like 'Z%';

It reports the following error:
ERROR: Invalid UNICODE character sequence found (0xc000)

I tried the same query on different tables in different databases -
gives the same error message.
The same error message appears to be even when the table is completely
empty!

Any ideas?
We run postgres 7.3.2 and default charset is UNICODE.

Cheers
Natasa