I used Flexviewer 1.3 on Flex Builder 3 for a while. I just downloaded Flash Builder 4 (trial version), and then imported my previous project. I compiled it, got several errors, as listed below: 1) In MagWidget.mxml - <mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" width="300" height="300" creationComplete="init()" mouseDown="mdEvent(event)" mouseMove="mmEvent(event)" mouseUp="muEvent(event)" backgroundAlpha="1.0" backgroundColor="#FFFFFF" borderColor="#000000" borderStyle="none" borderThickness="0" clipContent="true"> On the line of clipContent="true"> - Error message: The style 'borderThickness' is only supported by type 'mx.containers.Canvas' with the thems of 'halo' 2) Runtime error: ArgumentError: Error #1063: Argument count mismatch on mx.graphics::SolidColorStroke/apply(). Expected 3, got 1. at com.esri.ags.symbol::SimpleFillSymbol/traceExtent() at com.esri.ags.symbol::SimpleFillSymbol/drawExtent() at com.esri.ags.symbol::SimpleFillSymbol/drawSolidFillSymbol() at com.esri.ags.symbol::SimpleFillSymbol/drawFillSymbol() at com.esri.ags.symbol::SimpleFillSymbol/draw() at com.esri.ags::Graphic/drawWithSymbol() at com.esri.ags::Graphic/updateDisplayList() at mx.core::UIComponent/validateDisplayList() at mx.managers::LayoutManager/validateDisplayList() at mx.managers::LayoutManager/doPhasedInstantiation() at mx.managers::LayoutManager/validateNow() at mx.core::UIComponent/commitCurrentState() at mx.core::UIComponent/setCurrentState() at mx.core::UIComponent/set currentState() at com.esri.solutions.flexviewer::WidgetTemplate/init() at com.esri.solutions.flexviewer::WidgetTemplate/___WidgetTemplate_Canvas1_creationComplete() at flash.events::EventDispatcher/dispatchEventFunction() at flash.events::EventDispatcher/dispatchEvent() at mx.core::UIComponent/dispatchEvent() at mx.core::UIComponent/set initialized() at mx.managers::LayoutManager/doPhasedInstantiation() at mx.managers::LayoutManager/doPhasedInstantiationCallback() 3) The base widge and scale bar (on the left) appear to be not right (see the image attached). I guess they are related to the errors in 2). I wish someone can help for these bugs due to the software updating. Thanks.