Statistical tracking issue

I am running 8.3.7 on FreeBSD 7.0/amd64.

It appears that at some point about 2 weeks ago statistics tracking
ceased.

I have the following query which I use to track cache hits, and it is
not being updated:

SELECT pg_stat_database.datname, pg_stat_database.blks_read,
pg_stat_database.blks_hit, round((pg_stat_database.blks_hit::double
precision / (pg_stat_database.blks_read + pg_stat_database.blks_hit +
1)::double precision * 100::double precision)::numeric, 2) AS
cachehitratio

FROM pg_stat_database

WHERE pg_stat_database.datname !~ '^(template(0|1)|postgres)$'::text

ORDER BY round((pg_stat_database.blks_hit::double precision /
(pg_stat_database.blks_read + pg_stat_database.blks_hit + 1)::double
precision * 100::double precision)::numeric, 2) DESC;

blks_hit and blks_read values have not changed.

track_activities and track_counts is on. The result of the query is
shown below, but the values remain static. Same is the case with values
such as

"sessions";1819965;219050729;99.18

"ishield";12291564297;38928261045;76.00