Hi, I have a clickonce application (VS2010, .NET 4). I have registered a file association (.task), and this all works well. If I double click a file with the .task extension on the desktop the clickonce application opens and can open the file. If I email the file however, and double click the file from within outlook, I get the open/save dialog. If I click open nothing appears to happen. If I save the file I can open it by double clicking on it. Any ideas why the file does not open from within outlook ? Thanks, Mark