TabContainer activetab changed event is not firing

Hi all

I am using AjaxControlToolkit TabContainer for tabs and creating tabs dynamically in codebehind using C# and set 0 as active tadindex if not postback.

The error is

If it has multiple tabs and if I go to 2nd tab and third tab everythig is fine and  activetab changed event is firing but if I come back to 1st tab  activetab changed event is not firing.

Please some one help me.