Need help with PostgreSQL 8.3 workaround code

I'm getting the following error that I need help with:

* warning: pg_query() [function.pg-query]: Query failed: ERROR: operator does not exist: character varying = integer LINE 1: UPDATE users SET timezone_id = 311 WHERE timezone = -25200 A... ^ HINT: t(s). You might need to add explicit type casts. in /var/www/includes/database.pgsql.inc on line 139.
* user warning: query: UPDATE users SET timezone_id = 311 WHERE timezone = -25200 AND timezone_id = 0 in /var/www/modules/event/event.module on line 275.

I've seen similar errors get fixed with some modification of code, but I'm such a newb that i don't know where to begin.