Self-Join portal problem

I'm sure I'm being dumb here but here goes anyway.

I have a large database that has a single table ('Invoices') and the following fields:

invoice_no

account_no

invoice_date

type

input_date

I want to be able to search on any of the fields and display the results in a portal.

I've created a self-join relationship between the 'Invoices' table and a new table occurance called 'Invoices_2'. The relationship is invoice_no = invoice_no

When I do a search the results show fine in a standard list view, but the portal (showing records from Invoices_2 and set to display 25 rows) only displays 2 or 3 records per page.

For instance is I search on 444 in the invoice_no field, all of the records on each page match, i.e. all the records with invoice number 4441 are on the same page, all the records with invoice number 4442 are on another page, etc.

What I want is for it to display all the matching records on the same page.

I'm sure I've got it wrong somewhere but have run out of ideas!