Bruno, Try changing this line:AppEvent.addListener(AppEvent.WIDGET_RUN, checkIfLinkWidget);To this:ViewerContainer.addEventListener(AppEvent.WIDGET_RUN, checkIfLinkWidget);
AppEvent.addListener(AppEvent.WIDGET_RUN, checkIfLinkWidget);
ViewerContainer.addEventListener(AppEvent.WIDGET_RUN, checkIfLinkWidget);
Bruno,  You would only be getting this error if you are attempting to use this Flex Viewer 2.4 widget in an earlier version.
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