Commented Unassigned: error raising upload complete event and start new upload [27438]

I have the same issue as Brian Potter on http://stephenwalther.com/archive/2013/04/30/april-2013-release-of-the-ajax-control-toolkit. I have registered AjaxFileUploadHandler.axd in web.config but it makes no difference. I suspect there is a security issues but where? I don't have an App_Data and am trying to save to ~/Images but the error occurs at the start. The upload complete method is not reached.
Comments: Huh.. I've been struggling for a day to fix this issue.. :( :( Resolution suggested in few posts was to add -> <add name="AjaxFileUploadHandler" verb="*" path="AjaxFileUploadHandler.axd" type="AjaxControlToolkit.AjaxFileUploadHandler, AjaxControlToolkit"/> in handlers. I had added it in config like this - <system.webServer> <validation validateIntegratedModeConfiguration="false"/> <handlers> <add name="AjaxFileUploadHandler" verb="*" path="AjaxFileUploadHandler.axd" type="AjaxControlToolkit.AjaxFileUploadHandler, AjaxControlToolkit"/> </handlers> </system.webServer> But of no luck. Finally i found the actual resolution. It still adding the handler but in SYSTEM.WEB section as well like - <system.web> <httpHandlers> <add verb="*" path="AjaxFileUploadHandler.axd" type="AjaxControlToolkit.AjaxFileUploadHandler, AjaxControlToolkit"/> </httpHandlers> </system.web> This worked like a charm.. Refer to - http://stackoverflow.com/questions/16814310/ajaxcontroltoolkit-error-raising-upload-complete-event-and-start-new-upload for more info..