problem with remote_function and firefox 3

Anyone else having problems with remote_function and firefox 3? It
doesn't seem to make the AJAX call and firebug doesn't offer any info.
Doesn't reach the controller. Works ok in Firefox 2.

Thanks

<% remote_function :url => {:action => 'show_people'} %>
  <p><b>Projects</b><br />
    <%= collection_select(:project, :project_categories_id,
ProjectCategory.find(:all, :order => "name"), :id, :name, {:prompt =>
"-Select a category"}, :id => 'id_selected') %>
    </p>
    <%= observe_field 'id_selected', :url => {:action =>
'show_people'}, :with => 'id' %>