Is the immo light flashing when you try to start it? Any other warning lights on?
Is the car locking/unlocking with the remote?
Try here for your immo bypass code if you dont already have it. This is a temporary fix only, it has to be re-entered if the engine is off for more than ten minutes. Look in your handbook for entry instructions for your car, it seems to vary between models.
http://www.bba-reman.com/content.aspx?content=Test_for_Renault_Key_Immobiliser_failures_emergency_recode
laguna
October 2009