WaitOnLock: error on wakeup

Anyone know why I could possibly get this error? This doesn't happen
deterministically.

WaitOnLock: error on wakeup - Aborting this transaction

I also got this notice:

NOTICE:  Deadlock detected -- See the lock(l) manual page 

---

Actually, what I'm looking for in this mail is a possible way for me to
deterministically reproduce this by hand, to see if I can create this
situation and then look in my code to see where I could possibly be doing
the wrong thing. I'm not using anything fancy in my queries, Just foreign
key constraints (all initially deferred), Selects, inserts, updates, views,
transactions. No explicit lock or select for updates or triggers or notifiys
or rules.

I'm using Postgres 7.0.3.

BTW, i tried searching the mailing list and turned up nothing interesting. I
didn't search super carefully, because the search site is extremely slow.

Thanx!

-rchit