title: Cannot associate Simple Products in a Configurable
body: <p>I did an upgrade from 1.4.2 to 1.5.0 and realized that the product association in a Configurable product didn't work. After hours of rollbacks and testing I haven't found a solution. Even though I did a rollback to the previous version and database I couldn't get it back on track. I've tried to uninstall all extensions we have installed lately with the same result. This site is more or less based on Configurables so we are sort of stuck...</p>
  
  <p>I've found some details though;  </p>
  
  <ul>
  <li>Simple products created <em>before</em> the upgrade can be associated to a new Configurable product and existing ones.</li>
  <li>Simple products made <em>after</em> the upgrade can’t be associated to <em>any</em> Configurable product. </li>
  <li>When I create a new Configurable and make an association with the quick tool the new Simple product is created, but there's no insert to the database table catalog_product_relation for example.</li>
  </ul>
  
  <p>It seems that the Adminhtml is broken by something. I have no lead any longer so please fill in with suggestions what to look for.</p>