PostgreSQL type mismatch error

I am using postgresql. If I navigate to my subscription tab (/user/1/subscriptions/node), and click on pages/threads, I get the following:

PDOException: SQLSTATE[42883]: Undefined function: 7 ERROR: operator does not exist: integer = character varying HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.: SELECT c.* FROM {comment} c WHERE (c.nid IN (SELECT s.value AS value FROM {subscriptions} s WHERE (s.module = :db_condition_placeholder_0) AND (s.field = :db_condition_placeholder_1) AND (s.recipient_uid = :db_condition_placeholder_2) )) AND (c.uid = :db_condition_placeholder_3) GROUP BY c.nid; Array ( [:db_condition_placeholder_0] => node [:db_condition_placeholder_1] => nid [:db_condition_placeholder_2] => 1 [:db_condition_placeholder_3] => 1 ) in _subscriptions_content_node_form() (line 177 of /mysitepath/modules/subscriptions/subscriptions_content.admin.inc).