>>Did you try Fiddler to determine whether (a) or (b) above applies ?
>
>I am not familiar with Fiddler. It looks like a free tool to analyze the round trip of the hit to a server.

Get it :-}
It's a great tool for monitoring traffic to and from the browser. It would immediately tell you whether the request for the axd file was being made and show the response from the server (and a LOT more besides)

>
>>Did you check the IIS event log ?
>
>Are you making reference to the Event Viewer or another log? In the Event Viewer, I do not see anything wrong at this point.

I mean the IIS log.

>>Is the .axd extension registered on the server ?

>If you are talking about Web site\Properties\Home directory\Configuration\Mappings\Application extensions, then yes, .axd is there. It is presently registered to c:\windows\microsoft.net\framework\v4.0.30319\aspnet_isapi.dll with GET,HEAD,POST,DEBUG. If you are referencing something else, I do not know what this means.

I was thinking of the handler mappings in IIS (but, I admit, I'd be surprised if it was missing....)