Index: ps/trunk/source/gui/GUIManager.h
===================================================================
--- ps/trunk/source/gui/GUIManager.h
+++ ps/trunk/source/gui/GUIManager.h
@@ -59,9 +59,9 @@
 	shared_ptr<CGUI> GetActiveGUI() { return top(); }
 
 	/**
-	 * Returns whether there are any current pages.
+	 * Returns the number of currently open GUI pages.
 	 */
-	bool HasPages();
+	size_t GetPageCount() const;
 
 	/**
 	 * Load a new GUI page and make it active. All current pages will be destroyed.
Index: ps/trunk/source/gui/GUIManager.cpp
===================================================================
--- ps/trunk/source/gui/GUIManager.cpp
+++ ps/trunk/source/gui/GUIManager.cpp
@@ -73,9 +73,9 @@
 	UnregisterFileReloadFunc(ReloadChangedFileCB, this);
 }
 
-bool CGUIManager::HasPages()
+size_t CGUIManager::GetPageCount() const
 {
-	return !m_PageStack.empty();
+	return m_PageStack.size();
 }
 
 void CGUIManager::SwitchPage(const CStrW& pageName, ScriptInterface* srcScriptInterface, JS::HandleValue initData)
Index: ps/trunk/source/gui/scripting/JSInterface_GUIManager.cpp
===================================================================
--- ps/trunk/source/gui/scripting/JSInterface_GUIManager.cpp
+++ ps/trunk/source/gui/scripting/JSInterface_GUIManager.cpp
@@ -39,6 +39,14 @@
 
 void JSI_GUIManager::PopGuiPage(ScriptInterface::CxPrivate* pCxPrivate, JS::HandleValue args)
 {
+	if (g_GUI->GetPageCount() < 2)
+	{
+		JSContext* cx = pCxPrivate->pScriptInterface->GetContext();
+		JSAutoRequest rq(cx);
+		JS_ReportError(cx, "Can't pop GUI pages when less than two pages are opened!");
+		return;
+	}
+
 	g_GUI->PopPage(pCxPrivate->pScriptInterface->WriteStructuredClone(args));
 }
 
Index: ps/trunk/source/ps/Game.cpp
===================================================================
--- ps/trunk/source/ps/Game.cpp
+++ ps/trunk/source/ps/Game.cpp
@@ -320,7 +320,7 @@
 		g_NetClient->LoadFinished();
 
 	// Call the reallyStartGame GUI function, but only if it exists
-	if (g_GUI && g_GUI->HasPages())
+	if (g_GUI && g_GUI->GetPageCount())
 	{
 		JS::RootedValue global(cx, g_GUI->GetActiveGUI()->GetGlobalObject());
 		if (g_GUI->GetActiveGUI()->GetScriptInterface()->HasProperty(global, "reallyStartGame"))
Index: ps/trunk/source/ps/GameSetup/GameSetup.cpp
===================================================================
--- ps/trunk/source/ps/GameSetup/GameSetup.cpp
+++ ps/trunk/source/ps/GameSetup/GameSetup.cpp
@@ -1667,7 +1667,7 @@
 	LDR_Cancel();
 
 	if (g_GUI &&
-	    g_GUI->HasPages() &&
+	    g_GUI->GetPageCount() &&
 	    pScriptInterface->HasProperty(global, "cancelOnLoadGameError"))
 		pScriptInterface->CallFunctionVoid(global, "cancelOnLoadGameError", message);
 }