Bug with updateable Views and inherited tables?

Hello all,

i have a view defined as a simple select of a table.
This table is inherited by a couple of others.
All entries belong to the child-tables.

I also have an unconditional update rule on the view.
If i do an update to the view, the update is rewritten
to update the father-table.

And now a strange thing is happening:
If i do an update, this update is done correctly only
on the first defined child-table. If it applies to
one of the other 8 child-tables nothing happens at all.

If i update the father-table directly everything is
working like expected (the update is "directed" to the
right table).

Is this a known limitation with views, rules and
inherited tables i haven't heard of? Or is it a bug?

My Postgres is version 7.4.5.

Thanks in advance

Sebastian