Narrator Not reading the content in Ajax modal popup

We are using Ajax modal popup in our application to display the popup. 

After opening the popup, Narrator is not reading the popup content and still reading the background web page content tough it is disabled [ We are using windows 8 and Narrator shortcut key isCAPSLock + Ctrl + U which is used to read the entire webpage content automatically without using any other tab keys] 

Note: This functionality is working fine if we read through tab key or read line option (CAPSLOCK + ->) 

Please help me to read only the popup content when the popup is opened and withCAPSLock + Ctrl + U for narrator.

Thanks

Jeevitha