Book Access Module incompatibility

I'm trying to get the Book Access Module (http://drupal.org/project/book_access) running with my Drupal installation... using the RC1 build of the SQL driver. The error message comes about when I attempt to go to the Book Access UI, where I get the following error message:

PDOException: SQLSTATE[07002]: 
[Microsoft][SQL Server Native Client 10.0]COUNT field incorrect or syntax error: 
SELECT TOP(1) module FROM {variable_default} 
WHERE name = :name OR (:name LIKE CONCAT(name, '\_%') AND flags > 0); 
Array ( [:name] => book_access_default_authors_access ) 
in Vars->offsetGet() (line 286 of E:\content\sites\all\modules\vars\vars.module).

I'm not extremely familiar with the limitations of SQL vs. MySQL, but I'm guessing there's incompatible syntax at work here. I'm just not sure where.