Hi Simon,
Its says that you may need to explicitly typecast it. I had similar problem in content_item__new. You will have to hunt down the offending parameter or typecast all. What do I mean by that? If the parameter for example that needs to be typecasted is subscription_id here is how you will call it:
select na_subscription__new(
integer :subscription_id,
:user_id,
:feed_url,
:host_url,
:title,
:description,
'0',
current_timestamp,
'na_subscription',
current_timestamp,
:user_id,
:peeraddr,
:package_id
);
If explicitly typecasting it doesn't work... it must be another problem. Hope this helps.