rails toggle problem - ActionView::TemplateError (undefined method `[]' for #<Enumerable::Enumerator

Question

After this rails app has been running fine for over two years... just started getting this one error on only one page.

ActionView::TemplateError (undefined method `[]' for #<Enumerable::Enumerator:0xb25fbc4>) on line #10 of app/views/notes/_form.rhtml:
7:  <%= @n.text_field 'note', :size => 55  %>
8: </label>
9: <%= link_to_function('Custom Note', nil, :id => "custom_link", :class => 'control') do |page|
10:   page[:custom].toggle(:appear)
11:   page[:presets].toggle
12:   page[:custom_link].replace_html "Preset/Custom"
13: end %>

When I comment out lines 10 and 11, the lines with toggle, the page loads. But obviously doesn't do what I need.

Any suggestions on how to fix this?