Luis,
from the error message it appears that you are running OpenACS on PG 7.3.x. Unfortunately the reference packages haven't been ported to PG 7.3.x.
In order to patch the language package you would have to change acs_reference__new so that it accepts 'timestamptz' instead of 'timestamp' (without time zone).
However, be aware that other incompatabilities with PG 7.3.x might be lurking in this package and other none core packages.
/Bart