Renault Megane "electronic fault" display?

Hi. We have a petrol 1.6 Megane Expression on an 04 plate. Today I attempted to jump start another vehicle, connected the leads, started the Megane which powered the ignition lights in the car I was trying to start, but when I turned the key in the other car the Megane completely died. All lights on the instrument panel were lit, but there was no response at all from any attempt I made to do anything - it was completely dead aprt from the instrument panel being lit like a Christmas tree. I disconnected the battery and reconnected, the car is now completely dead - nothing at all evokes a response. Help!!!!