If you have upgraded the PDA plugin in past 2 days you might run into header output issues which might break the operation of wordpress where ever header function was being used.
To overcome the issues please de-activate the plugin and upgrade the plugin to the latest version 1.2.6 and activate the plugin back.
This error was due to some unwanted junk character present in the beginning of the file. It was due to the editor issue which I had used to save the file and commit the file to the repository.
I am really sorry for causing this issue and sorry for the inconvenience caused 🙂