Could you check to see if either of the code snippets below helps you get the job done?
ExecuteOrDelayUntilScriptLoaded(function () {
SP.UI.Notify.addNotification("YOURMESSAGE", false); },"sp.js");
or
parent.ExecuteOrDelayUntilScriptLoaded(function () {
parent.SP.UI.Notify.addNotification("YOURMESSAGE", false); },"sp.js");
Also, be sure to check for javascript errors by using a debugger. (In IE you can do it by enabling the "Developer Tools" feature and pressing "start debugging" button in the Script tab, In firefox you can use the Firebug plugin)