ASP Recordset Filter Failure

With the following code snippet:

<%="complexid =" & rsComplex("ComplexID")%>
<% rsPhoto.filter = "complexID =" & rsComplex("ComplexID") %>
<%response.Write("<br>ID: " & rsPhoto("complexID"))%>

I get an 80020009 error on the last line.

The first line appears in the HTML output as complex=589, so I know
that there is a valid value available for the filter.

This worked once and hasn't worked since.

The rsPhoto recordset is viewable in a seperate page. The complexID in
the associated table has a value of 561 in the complexID column.