Rule problem

All,

given this rule:

create rule add_upref_os as on insert to upref_os do
update gen_stats set total = total + 1 where os_id=current.os_id;

and this insert....

insert into upref_os values(1234,2);

gives me this error continuously until I cancel the query:

NOTICE: Non-functional update, only first update is performed
NOTICE: Non-functional update, only first update is performed
NOTICE: Non-functional update, only first update is performed

I'm running 6.4. Any ideas? I've got other rules that seem to function without
issues...

-=pierre