Locking or Something Else?

I have a situation where an increase in volume of inserts into the
main transaction table causes a huge slowdown. The table has lots of
indexes and foreign keys and a trigger.

Clearly, something is causing a resource contention issue, but here's
my main question:

I have log_lock_waits = on and deadlock_timeout = 250ms. Is there
any way I could have delays of tens of seconds caused by a write
conflict in a table accessed by a trigger that would not result in the
wait being logged?

Thanks!

Ian
PostgreSQL 9.0.6 on x86_64-unknown-linux-gnu, compiled by GCC gcc
(GCC) 4.1.2 20080704 (Red Hat 4.1.2-46), 64-bit