car wont start?

I have an R reg Megane, it was not used for 2 weeks and when I went to use it it started first time and then it wouldnt go again. I heard a sizzling sound when inside the car. the engine turns but wont start, the lights work but the nothing else. checked battery its fine, changed fuses and tried another key and still none of the electrics are working, never had any probs b4, at wits end please help. ps could it b immobiliser problem