Problem with pgstat timneouts

About a month ago, I started receiving quite a few pgstat timeouts on my
production database.

PostgreSQL 9.0.3 on amd64-portbld-freebsd8.1, compiled by GCC cc (GCC)
4.2.1 20070719 [FreeBSD], 64-bit

I am not sure where to start looking for the cause.

Database has been up since march without any restart

db1# ps -aux | grep stat

pgsql 1287 1.0 0.0 22832 4724 ?? Ss 11Mar11 4265:13.87
postgres: stats collector process (postgres)

It appears that these timeouts are affecting the performance of the
application - sometimes it hangs for a few seconds before data gets
returned, which was not the case before this.

2011-12-22 03:45:04 MST WARNING: pgstat wait timeout

2011-12-22 03:45:04 MST WARNING: pgstat wait timeout

2011-12-22 03:45:04 MST WARNING: pgstat wait timeout

2011-12-22 03:45:04 MST WARNING: pgstat wait timeout

2011-12-22 03:45:41 MST WARNING: pgstat wait timeout

2011-12-22 03:45:41 MST WARNING: pgstat wait timeout

2011-12-22 03:45:41 MST WARNING: pgstat wait timeout

2011-12-22 03:46:18 MST WARNING: pgstat wait timeout

2011-12-22 03:46:18 MST WARNING: pgstat wait timeout

2011-12-22 03:47:32 MST WARNING: pgstat wait timeout

2011-12-22 03:47:32 MST WARNING: pgstat wait timeout

2011-12-22 03:47:32 MST WARNING: pgstat wait timeout

2011-12-22 03:48:09 MST WARNING: pgstat wait timeout

2011-12-22 03:48:09 MST WARNING: pgstat wait timeout

2011-12-22 03:48:09 MST WARNING: pgstat wait timeout

2011-12-22 03:49:26 MST WARNING: pgstat wait timeout

Runtime statistics setting for the database are as follows:

#-----------------------------------------------------------------------
-------

# RUNTIME STATISTICS

#-----------------------------------------------------------------------
-------

# - Query/Index Statistics Collector -

#track_activities = on

#track_counts = on

#track_functions = none # none, pl, all

#track_activity_query_size = 1024 # (change requires restart)

# On FreeBSD, this is a performance hog, so keep it off if you need
speed

update_process_title = off

#update_process_title = on

#stats_temp_directory = 'pg_stat_tmp'

# - Statistics Monitoring -

#log_parser_stats = off

#log_planner_stats = off

#log_executor_stats = off

#log_statement_stats = off