VW Golf mk4, central locking?

The central locking on my mk4 golf has suddenly stopped working. When I push unlock button on key fob, it only unlocks the boot, same for when I lock it. The central lock and unlock buttons on the inside of the drivers door (next to window buttons) does the same thing, only effecting the boot. I can lock and unlock the doors individually but hoped there was a way to fix this problem. Thanks in advance.