This application uses ATLAS to provide the AJAX user interface, and presents three link buttons that call methods both asynchrounously and synchronously on the server with the ScriptTimeout property set really low to simulate long running request problems.   It also uses a cool feature of ATLAS, the TimerControl, to provide the polling code necessary to update the UI and show a progress bar.  Download the code here to try it out for yourself.  I’ve had to rip out the ATLAS script stuff because of the ATLAS eula, but download ATLAS, an copy the Microsoft.Web.Atlas.dll ot the bin directory, and the Scripts to the ScriptLibary directory and you should be able to experiment with this code.