An A319 Captain noted an avionics vent fault ECAM prior to departure. Maintenance deffered the the fault via the MEL and released the aircraft. During climb through 6;000 FT; an ECAM status message not to exceed 10;000 FT was received. Flight returned for an overweight landing.

Narrative

During the boarding processes we received an avionics vent fault ECAM message. It was twenty minutes before departure and we put the discrepancy in the Log and called Maintenance. Maintenance was quick to respond and mentioned that this particular aircraft had this fault ten times in the last thirty days. The mechanics decided to MEL the system; and signed the log after completing the follow up procedure. We took off about one and a half hours late. During climb through 6;000 FT; we received an ECAM status message not to exceed 10;000 FT in the climb. We notified Maintenance and also sent an ACARS message to our Dispatcher and returned to the field for an overweight landing at 143;600 LBS. The sink rate at touchdown was 200 FT per minute. Maintenance said they would have the MEL corrected and we would soon be on our way. I spoke via phone with the assistant Chief Pilot and with his approval; I decided to get another aircraft. We departed and the trip was uneventful. Maintenance improperly applied the MEL.