The certificate module was updated recently and then a student logged in and got these errors in the Recent Activities Block related to the workshop logs.

SELECT l.time, l.url, u.firstname, u.lastname, a.workshopid, a.userid, e.name FROM mdl_log l, mdl_workshop e, mdl_workshop_submissions s, mdl_workshop_assessments a, mdl_user u WHERE l.time > 1273549600 AND l.time < 1273720637 AND l.course = 2613 AND l.module = 'workshop' AND l.action = 'agree' AND a.id = l.info AND s.id = a.submissionid AND a.userid = 62 AND u.id = s.userid AND e.id = a.workshopid;
ERROR: operator does not exist: bigint = character varying at character 306
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
LINE 1: ...dule = 'workshop' AND l.action = 'agree' AND a.id = l.info A...

Works fine with patch applied to make the where clause "a.id = l.info" cast correctly in PostgreSQL - "a.id = CAST(l.info AS INT)"