PLEASE HELP AGAIN. How do I manage add-ons if the menu item is dimmed in Internet Explorer 9. Thank you as you gave the the answer before and I cannot find the reply and this keeps happening.
Sure Beverly – Click the little gear symbol to the far right of your browser windows and choose Internet Options from the drop-down menu.
This window will open.
Select the Advanced tab to the far right of the window.
Now scroll down to the Browsing section. It’s a long list, so look carefully.
Make sure that Enable third-party browser extensions is checked.
Hit OK to save the change and restart your computer for it to take effect.
Now if this keeps happening and you haven’t made any changes to your Internet Options, there might be an issue with your profile and you may need to create a new one. Microsoft has some helpful instructions for creating a new Vista profile here. 
Let’s hope one of these options takes care of your issue.