Problem with handling exception when sending data by ajax with jQuery

i got following part of one of functions

        if(continiueSend)
        {
            $.ajax
            ({
                type: "POST",
                url: "mailer.php",
                data: "somestestdata",
                timeout: 5000,
                success: function(a) 
                {
                    alert(a);
                },
                error: function (xhr, ajaxOptions, thrownError)
                {
                    alert(xhr.status);
                    alert(thrownError);
                }    
            });
        }

And it works great when server is ok, requested data are sent in less than 100ms, in case when i turnoff sever it also works great,script reports errors as it expected, but there is problem when server is busy

When time of sending data exceeds limit set with "timeout:" error handling as specified in "error:" isn't fired, and in console appears following information

uncaught exception: [Exception... "Component returned failure code: 0x80040111 (NS_ERROR_NOT_AVAILABLE) [nsIXMLHttpRequest.status]" nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)" location: "JS frame :: http://127.0.0.1/site/index.php?article=2 :: anonymous :: line 252" data: no]

Line 252 is first line of mentioned code. I tryied to put code inside IF brackets into try...catch but with no results.

How I can properly detect this exception to handle it the way i want?

MTH

Are you sure the error callback isn't actually called? Place a try-catch block inside the error function. Remember, this is called asynchronously. A try-catch block outside of it won't do anything. Probably the exception is caused when you try to read the error.