1996 Audi A4 Automatic

Hi there,
Please I wonder if you could help me. I have noticed that the central locking system on the audi a4 auto doesnt seem to lock the doors anymore. It beeps as though it is locked but the knobs do not go down and infact the doors are not locked. They can still be opened which inturn sets off the alarm. Please help. There also seems to be a long weird noise coming from the back area of the car when the key is used to lock the door on the outside. Is this something that I can fix on my own?!