If you're experiencing windows not always rolling down when you press the switch and errartic locking of the doors, the security module might be at fault. You can find this little module behind the battery in the trunk. If you release the tabs around the edge that held it together and open the two halves, you'll see a circuit board. You can lift the circuit board out of the plastic case, but there is a small, thin four-wire flat cable that runs from the circuit board to another piece linked to the antenna plug.
Lift part of a two piece white fixture that the cable connects to at each end to remove the tips of the cable and clean the tips of both ends before reattaching them into the white fitting on each component. That should do it.