After installing the extension and activating it for the target company and logging in to it, go to Setup -> Access Setup -> System Administrator -> tick the permissions and save the role. Logout and login again. Choose the dropdown theme and see if the Import CSV is greyed out. If so, visit the Setup -> Access Setup page and then see if the menu item is visible. This problem does not exist in the Canvas and Default themes as they do not use the meta forward to go to the dashboard.php file.
Just tested it out again for both the original and the patched versions of the extension.
Checked in the apache error logs and the tmp/errors.log - nothing there.
@joe: can confirm that when switching back and forth from / to the dropdown theme, the import_items extension (original) does get disabled without error but visiting Setup -> Access Setup page seems to re-enable it when done from the said theme itself.