waiting for ExclusiveLock on extension of relation

Hello --

I'm seeing some odd warning in my postgres (8.3.6) logs.

2009-06-01 20:01:59 UTC (10.11.199.136)LOG:  process 7070 still
waiting for ExclusiveLock on extension of relation 43911 of database
43623 after 1001.240 ms
2009-06-01 20:01:59 UTC (10.11.199.136)LOG:  process 7070 acquired
ExclusiveLock on extension of relation 43911 of database 43623 after
1335.801 ms
2009-06-01 20:02:29 UTC (10.11.199.136)LOG:  process 6971 still
waiting for ExclusiveLock on extension of relation 43862 of database
43623 after 1001.076 ms
2009-06-01 20:02:30 UTC (10.11.199.136)LOG:  process 6971 acquired
ExclusiveLock on extension of relation 43862 of database 43623 after
1979.106 ms

Googling around I've seen mention that this sort of lock is indicative
of waiting for a new btree index page to be created on disk (see:
http://archives.postgresql.org/pgsql-hackers/2004-11/msg00314.php)

Yet I'm surprised this is taking > 1 full second with some frequency.

My questions:
  (1) how worried should I be about this?
  (2) what can/should I do to alleviate/prevent this issue?

thanks in advance,
- Mason