Deferred constraints and locks...

Hello - Trying to track down a lock contention problem, I have a process
that does a series of select / insert operations. At some point the
process grabs a series of RowExclusiveLock(s) and has the obvious effect
of stalling other processes. I logged all the statements and don't see
any for update or explicit lock statements. So I am guesses this is more
of an internal design issue. All the FKEY constraints are deferrable and
initially deferred, could this be causing pg to be pulling locks on rows
that are part of the fkey? Something else I should be looking for?

Thanks!
-Nate