I've chack the ground wires are good, but on my mrssage box on dashboard says mobilizer illuminator or something like that.....thanks

Do you have another key you can try? If it starts with the other key then you have a faulty key. If you only have one key then you need to look at the Central Electronic Module parameters under immobolizer to see if it is sending a valid key code? You may want to call Volvo to see if they are participating in the Volvo Service for life program. Let them know the immobolizer light is on and it wont start. Here is a link for more info.
http://www.volvocars.com/us/top/yourvolvo/volvoserviceforlife/pages/default.aspx
Good luck to you and let us know what happens.