Image styles are not getting created Our image styles are not getting created on one of the Drupal 7 sites in a multi-site installation. They are created for at least one of the other sites that uses the same Drupal 7 core.

Symptoms: Upon uploading an image to a node, the image preview does not get displayed (depending on the browser, a broken image placeholder may display). The image is not created in the file system either. I have verified file system ACLs. Both sites use the same .htaccess.
As per image style (imagecache) images are not being created, changing the theme and reverting back fixed the problem. Very strange - it would be nice to know what the cause was!