Adding New Menu Items Causing Problems in Loading

Hello !
I have installed Joomla 1.5
Search Engine Friendly URLs Yes
Use Apache mod_rewrite yes
Add suffix to URLs No

Before installing mobile joomla, my website menus have been loading qutie nicely.
Now when i try to add new menu items in it after creating new articles, then I get the page not found error.

When I put my cursor on the faulty menu item through the live website, then it read like this:"
www.oursite.com/en?Itemid=157&option=
Whereas, my older menu items are working fine, and when I put cursor on them, it reads like this
www.oursite.com/en/category/article


When I try to put the address of the defected menu item on the address bar directly,
www.mysite.com/ index.php?option=com_content&view=article&id=77
Then it works fine and this page gets loaded by this easily.

I am unable to add new articles working in to the menus.



How can i resolve this issue. ?


Thanks & Best Wishes.