Problems with "anyelement" after upgrading from 8.1.4 to 8.1.9

Hello

I am using an application that has this function defined in the database:

Schema | Name | Result data type | Argument data types |
Owner | Language | Source code | Description
--------+------+------------------+---------------------------------+------------+----------+-------------+-------------
public | if | anyelement | boolean, anyelement, anyelement |
drupal | sql |
SELECT CASE WHEN $1 THEN $2 ELSE $3 END;

This function is used in some select queries, for example:
SELECT n.nid, IF(l.last_comment_uid != 0, cu.name, l.last_comment_name)
.......

Until postgresql 8.1.4, this has been working without problems.
Yesterday I upgraded this database to 8.1.9 and select queries using the
IF function fail with this error message:

ERROR: cannot display a value of type anyelement

Any idea why this happens and how we can fix it?

Thanks in advance.
--
Rafael Martinez, <r(dot)m(dot)guerrero(at)usit(dot)uio(dot)no>
Center for Information Technology Services
University of Oslo, Norway

PGP Public Key: http://folk.uio.no/rafael/>