array_shift(): The argument should be an array

Drupal installation upgraded to 4.7.0, trackback.module from CVS. Trying to call www.site.tld/admin/trackback/approval returns an empty page and dumps hundreds (literally!) of messages into the log that look like this:

Location http://www.site.tld/admin/trackback/approval
Referrer http://www.site.tld/admin/trackback
Nachricht array_shift(): The argument should be an array in /home/sites/site138/web/includes/form.inc on line 469.
Severity error

The discussion at http://drupal.org/node/62027 suggests this is an API problem.