Clojure/JDBC/Postgresql: I am trying to update a timestamp value in postgresql from a string, getting an error

Using the clojure jdbc library with postgresql. I have a table "xxx" with a timestamp column "created_at" in postgresql, and I have a string containing a date in the right format. Doing an insert fails:

(require '[clojure.java.jdbc :as sql])

(sql/with-connection *db*
  (sql/insert-record :xxx {:created_at "Thu Feb 09 10:38:01 +0000 2012"}))

Here is the error:

org.postgresql.util.PSQLException: ERROR: column "created_at" 
is of type timestamp with time zone but expression is of type character varying

So I understand that postgres requires a timestamp value, but how do I convert my string representation of the date into something postgres will accept? java.util.Date fails also, and I can't find any docs on the clojure postgres library.

Thanks!