Delete Cascade FK speed issue

Hi,
    I've dbase with about 80 relations.
    On deleting a user, this cascades through all the tables.
    This is very slow, for 20 users it takes 4 hours, with exclusive
access to the dbase.
    No other users connected to the dbase.

    Ok I know there will be somewhere a relation with a FK without
index, which
    is being scanned sequentially. But how can I find out what postgres
is doing
    while it is handling the transaction?

    Is there a way I can find out what postgres does, and where it hangs
around, so I know
    where the FK might not be indexed. (The dbase is to big to analyze
it by hand).

    The  way I do it now is to check the pg_locks relation, but this is
not very representative.

    Is there profiling method for triggers/constraints, or a method
which gives me a hint
    why it is taking so long?

thanks in advance