Page_Init() being called twice - asp.net

Question

The Page_Init() method of my page is being called twice before it is first displayed. In both cases, IsPostBack==false. I have AutoEventWireup="true" set. Here are the two stack traces for when it's being called:
First call:
G2.dll!Ctron.UI.Common.BreakoutDialog.Page_Init(object sender, System.EventArgs e) Line 46 C#
System.Web.dll!System.Web.Util.CalliEventHandlerDelegateProxy.Callback(object sender, System.EventArgs e) Unknown
System.Web.dll!System.Web.UI.Control.OnInit(System.EventArgs e) Unknown
System.Web.dll!System.Web.UI.Page.OnInit(System.EventArgs e) Unknown
CXGlobal.dll!Ctron.UI.CtronDialog.OnInit(System.EventArgs e) Line 27 C#
System.Web.dll!System.Web.UI.Control.InitRecursive(System.Web.UI.Control namingContainer) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequest(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequest() Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequestWithNoAssert(System.Web.HttpContext context) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequest(System.Web.HttpContext context) Unknown
App_Web_g2ej3jrk.dll!ASP.common_breakoutdialog_aspx.ProcessRequest(System.Web.HttpContext context) C#
System.Web.dll!System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() Unknown
System.Web.dll!System.Web.HttpApplication.ExecuteStep(System.Web.HttpApplication.IExecutionStep step, ref bool completedSynchronously) Unknown
System.Web.dll!System.Web.HttpApplication.ApplicationStepManager.ResumeSteps(System.Exception error) Unknown
System.Web.dll!System.Web.HttpApplication.System.Web.IHttpAsyncHandler.BeginProcessRequest(System.Web.HttpContext context, System.AsyncCallback cb, object extraData) Unknown
System.Web.dll!System.Web.HttpRuntime.ProcessRequestInternal(System.Web.HttpWorkerRequest wr) Unknown
System.Web.dll!System.Web.HttpRuntime.ProcessRequestNoDemand(System.Web.HttpWorkerRequest wr) Unknown
System.Web.dll!System.Web.Hosting.ISAPIRuntime.ProcessRequest(System.IntPtr ecb, int iWRType) Unknown
System.Web.dll!System.Web.Hosting.ISAPIRuntime.System.Web.Hosting.IISAPIRuntime2.ProcessRequest(System.IntPtr ecb, int iWRType) Unknown
[AppDomain Transition]
Second call:
G2.dll!Ctron.UI.Common.BreakoutDialog.Page_Init(object sender, System.EventArgs e) Line 46 C#
System.Web.dll!System.Web.Util.CalliEventHandlerDelegateProxy.Callback(object sender, System.EventArgs e) Unknown
System.Web.dll!System.Web.UI.Control.OnInit(System.EventArgs e) Unknown
System.Web.dll!System.Web.UI.Page.OnInit(System.EventArgs e) Unknown
CXGlobal.dll!Ctron.UI.CtronDialog.OnInit(System.EventArgs e) Line 27 C#
System.Web.dll!System.Web.UI.Control.InitRecursive(System.Web.UI.Control namingContainer) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequest(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequest() Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequestWithNoAssert(System.Web.HttpContext context) Unknown
System.Web.dll!System.Web.UI.Page.ProcessRequest(System.Web.HttpContext context) Unknown
App_Web_g2ej3jrk.dll!ASP.common_breakoutdialog_aspx.ProcessRequest(System.Web.HttpContext context) C#
System.Web.dll!System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() Unknown
System.Web.dll!System.Web.HttpApplication.ExecuteStep(System.Web.HttpApplication.IExecutionStep step, ref bool completedSynchronously) Unknown
System.Web.dll!System.Web.HttpApplication.ApplicationStepManager.ResumeSteps(System.Exception error) Unknown
System.Web.dll!System.Web.HttpApplication.ResumeStepsFromThreadPoolThread(System.Exception error) Unknown
System.Web.dll!System.Web.HttpApplication.AsyncEventExecutionStep.OnAsyncEventCompletion(System.IAsyncResult ar) Unknown
System.Web.dll!System.Web.HttpAsyncResult.Complete(bool synchronous, object result, System.Exception error, System.Web.RequestNotificationStatus status) Unknown
System.Web.dll!System.Web.SessionState.SessionStateModule.PollLockedSessionCallback(object state) Unknown
mscorlib.dll!System.Threading.TimerQueueTimer.CallCallbackInContext(object state) Unknown
mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Unknown
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Unknown
mscorlib.dll!System.Threading.TimerQueueTimer.CallCallback() Unknown
mscorlib.dll!System.Threading.TimerQueueTimer.Fire() Unknown
mscorlib.dll!System.Threading.TimerQueue.FireNextTimers() Unknown
mscorlib.dll!System.Threading.TimerQueue.AppDomainTimerCallback() Unknown
[Native to Managed Transition]
The difference happens at the point where System.Web.HttpApplication.ResumeStepsFromThreadPoolThread() calls ResumeSteps() again and that eventually calls Page_Init() again.

Answer 1

Two things that have caused this to happen to me;
You have a blank src element in a HTML image tag that effectively makes another request to the same page. For example,
Two lots of events wired up. In VB this happens when you have an explicit handles clause on a method and it is also wired up via the designer. You might prefer to wire up your events explicitly and turn off auto event wireup (this goes for C# too).
It could be many things, but the img tag happens a lot.