How can I fix my CL on a Vaux Zafira 00?

Locked the car yest it made a couple of noises but locked. Went to use in the aft and had to use key to open and the front pass door wouldn't unlock at all. The back doors have been a bit iffy for while but don't use them much these days so no real prob for us just pull the button up from inside. Any ideas what would suddenly cause the problem?