Ok here goes... we have a similar problem...

Our switch goes off, but it won't even let us turn it back on even after I've turned all the switches off. We have to hold it a certain way and turn it on very slowly to allow the power to go back on. I've unplugged things like fridge/computers etc but it still happens, I've also turned off all the power switches and it still won't go back on. Any idea what it could be? We spoke to the RE to come out and have it checked, and the sparky that the RE uses said it sounds like an appliance and probably the fridge and they'd have to charge us to find out what it is. And at $100/half hr I would rather try and be 100% sure its not our fault before him coming out. It just seems weird to me that the switch won't turn back on.