I am Running SharePoint 2010 Site , recently we migrated Web App from Development Server to Production Server(Different Domain Controller). In Development Server I used to be able to Use People Picker Everywhere.

But Now In production Server It searches for the AD Users. I can See them, but when i try to select and add users it doesnt Resolve.

This Functionality is only affected Site Collection Level. Other Site Collections in Same Web Application are working fine. its just this site.

Weird Problem is , I took backup of the Site Collection In production server and created new web app in my old Dev Server and Restored backup, It worked Fine Again There.

Please Help If Anyone has ever run into this situation.

Thank You