Notifications occuring differently

Hi,

 We are using project server 2007. All these days project managers used to get notifications in the following way

  Ex: A project manager assigns 3 different tasks in a project to the team member. Team member receives notification and then updates time in 3 different lines in timesheet. Once timesheet is submitted(all 3 lines) by team member, the manager now gets one email containing all these 3 tasks and status as notification.

Suddenly today we observed that project manager is receiving 3 separate emails for 3 different tasks for a single project, which is really bothering the managers. What could be the reason, is there any settings as such which we can change to start receiving only one email as before.

Thanks

mp