Fatal error: Cannot access empty property on result->fetchAll(PDO::FETCH_OBJ)

ON: SQL Server 2008 R2

When trying to activate the WP Groups plugin (http://ww.wp.xz.cn/plugins/groups/), I get Fatal error: Cannot access empty property on the following line (drivers/pdo.php, _post_query() method):

$this->last_result = $this->result->fetchAll(PDO::FETCH_OBJ);

I tried checking for null, empty, property_exists, method_exists on result and fetchAll() prior to that line so I could log the query that is causing the problems and none of my checks ever returned false. Could this be a problem internally in the fetchAll() method?

When logging all queries the last one logged before the fatal error is:

12/16/13 19:34:33,788 [7068] DEBUG pdo_wpdb - PDOStatement::__set_state(array(
   'queryString' => 'SELECT @@IDENTITY',
))

SELECT @@IDENTITY executed without error earlier so I can not say with confidence that it is the culprit.

I’ve spent a few hours on this and can’t figure it out. Any suggestions?

http://ww.wp.xz.cn/plugins/wordpress-database-abstraction/