ELCB keeps switching off

Since a few weeks the ELCB in my fuse box switches off at random, however it was just a matter of switching it back on and it would work again.Every time it reminded me to get an expert in to fix it, and every time the urge for the expert passed when it worked again.
So, now it is Saturday night, and it stopped working for good it seems.
No socket in my house works and the fridge&freezer will be at room temperature when I wake up. Time for a little panic.... Chances of getting an expert in on Sunday will be close to zero, so is there anything I can do without getting myself killed ?
Some facts:

• There have been no extra appliances connected and it worked fine before
• The switch does not let it self be switched back on, even without the individual fuses for all sockets in the off - position
• House is 4 years old

For some reason I think (guess, hope) that the ELCB switch itself is faulty and that I might be able to get a new one in B&Q or so tomorrow and even might change it and this is where it probably gets dangerous.

Can someone help me by suggesting what might be wrong, why I should not try anything myself and where I could get some professional help on a Sunday?

Unplug everything, then reconnect the devices one by one to see what triggers the switch. If you keep your fridge/freezer doors closed, they won't be hugely affected.

Thanks RainyDay, will do as I have nothing better to do. But if I have all my fuses turned off , how can there be a current going to the appliances causing the ELCB to switch off ?
Thank God for laptop batteries and gas cooking

Well, it worked...At first it didn't, but then I realised there is a socket in my shed servicing my water treatment and pump installation. Unplugged those plugs and hurray, the ELCB has not switched off now for half an hour. The unfortunate thing is that my freezer tells me the temperature is +3 degrees and that I now don't have fresh water ( and that obviously my tank will be running out at some point). Thanks for your help and I will be starting a new thread about my water installation as I have nothing but trouble with it.
One thing that keeps bugging me is that the fuse for the water installation has not tripped this time (it normally and regularly - once a month or so does).

Hi. The ELCB (or RCD?) is for detecting current leaking to earth from your live or neutral. This current could be well below what your fuse (MCB?) is rated for. So, if you have a dodgy pump/cable, you could be getting a mixture of both fault scenarios.

The fuse/MCB is solely to protect against a higher current flow in the live wire than what the cable is rated for.