WaitOnLock error on wakeup

I am getting a WaitOnLock error on wakeup when searching my database
using php on my website. This is clearly a pgsql error message, but I
can't seem to understand why pgsql would lock on me.

My problem query returns batches of 100 found products and I keep
statistics for each product found. Therefore, there is 100 writes to the
db for each query. My code causing the error looks like:
update product_table set stat='$x' where id='$id';

My current OS and software are:
Freebsd 3.3-CURRENT with the following ports:
apache+php+mod_ssl-1.3.9+3.0.12+2.4.2
postgresql-5.4.1

I am running postmaster with the following flags:
postmaster -i -S -o -F

Thanks in advance,
Marc