I'm currently having a problem (seems to be related to my new stereo, god knows how a stereo controls the door locks :P ), whenever my new stereo is plugged in the drivers door seems to randomly unlock itself. Are you sure that when you unlock it, it is actually unlocking all four doors and that the drivers door is not unlocked already (therefore, the first stage of the unlocking has already completed, as when you press the remote once it is actually carrying out the second stage of unlocking the rest of the doors). I haven't found a reason/explanation for this yet, and I know its a long shot for you, but by chance it could be something similar? Anyone one here know if central locking systems are common problems on these Corsa's?
Hope that helps.
Karl
November 2007