When your partial template just won't display, you might have done what I did!
If the development.log shows it is rendered, but you see absolutely nothing in the page source or on the borwser, you proably did what I did.
I left out the "=".
<% render :partial => "shared/file" %> is processed, but produces no output!
If you add the "=" to make:
<%= render :partial => "shared/file" %> it works just like you expected!!
Key words: partial, template, render, fail, missing, no output