SharePoint Task List email notifications does not work after modification of Items

I had a problem with  SharePoint Task List and the assignTo field for email notifications while modifying the task.
Its not sending any mail neither to assignedTo nor to created By.

After googling, I used the follwing steps:

1. Confirm that the webapplication of the site collection to which you have imported the site has the correct Outgoing Email Configuration. - Found OK
2. Run stsadm -o getproperty -url http://site  -pn alerts-enabled
   The expected output is <Property Exist="Yes" Value="yes"/>. If its not Yes then need to enable it with  command: stsadm.exe -o setproperty -pn alerts-enabled -pv "true" -url http://site -Found OK
3. If everything is there as expected but still emails not working then as Jack mentioned run
   stsadm -o updatealerttemplates -url http://site -f C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\XML\Alerttemplates.xml –LCID 1033. - and that was the issue. Now its working fine.

The default timer interval is 5 minutes. Thus, if this interval has not been changed you could notice a delay of up to 5 minutes (the default timer interval) before an alert message is generated. Changes are recorded as they occur in an event log (discussed later in this article) and then alert messages are rendered from that log when the next timer job runs.

         So, I have also checked the default timer interval property of alert using stsadm command:

         stsadm -o getproperty -pn job-immediate-alerts -url http://site

 

        and reset it to 3 min using stsadm command:

       stsadm -o setproperty -pn job-immediate-alerts -url http://site -pv "every 3 minutes"