WP-admin pages not loading. Unable to edit.

Dashboard loads fine but other admin pages unable to load.

No data received
Unable to load the web page because the server sent no data.
Here are some suggestions:
Reload this web page later.
Error 324 (net::ERR_EMPTY_RESPONSE): The server closed the connection without sending any data.

I’m unable to load the plugins or other pages to troubleshoot at all. This is the same with Chrome, Explorer & Firefox.

This only happened after editing a page with the following code;
<iframe src=”http://www.bestdojo.net/student/mobile-login.asp?lang=1″ name=”frame3″ scrolling=”auto” frameborder=”no” align=”center” height=”500px” width=”700px”></iframe>

I’m unable to even edit the same page to undo.

Please advice, I’ve goggled and found nothing helpful for my case.