Insert Rule, Multiple Insert, Update Problem

Hi,

I am having trouble with an insert rule that also does an update. It works
fine for a single insert but multiple inserts in a single statement don't
behave as I expected.

An outline of the problem is:

A table "trans" has a "client_id" and a transaction amount called "points".
Another table "clienst" also holds the "client_id" and an accumulated
amount "total_points". I create a rule for the trans table:

create rule trans_insert as on insert to trans do also
updateclients
set       total_points = total_points + NEW.points;
where   client_id = NEW.client_id;

This works fine for a single insert but if I dump multiple transactions for
multiple clients in the trans table only the first transaction for each
client is accounted for in clients.total_points.

I am just about to try and implement this as a trigger but it is driving me
crazy as to why this won't work as a rule. If I put something like the
following:
insert into foo values(NEW.points);

Then every transaction points value is copied to foo.

Any help is very appreciated.

Thanks,

Scott.