Basically what autoeventwireup does is allow you to either manually bind events or allow VS to do it for you. if it is set to true then VS will add the Button1_Click() event for you and if it is false, you will have to bind it yourself.

Is any of your controls set to autopostback on change? For example, if you have a textbox that is set to postback when you hit enter and you click the submit button. that can cause it to be hit twice.

another possibility is that if you have a page passing control to another page by using server.transfer instead of response.redirect could yield your double init and load