Admin Panel Stalls

I ran an update of WordPress to the new 3.8 and that is when the admin panel began to stall. The admin panel loads fine but when ever I try to select a sidebar button such as Users, Plugins etc. The panel stalls with a greyed out screen and progress bar. If I click on the screen that disappears but I still can not do anything. If I try to click again on a sidebar selection or even try to logout I get the grey screen with the progress bar that never ends….

In efforts to resolve the issue:
I have downloaded various previous versions of WP deleted the Wp-admin & WP-includes and have uploaded all new files included with the versions.

I have tried removing plugins and bypassing the current theme so it will default to a standard WP theme. Nothing works.(We are running WP Flexishop12 Theme)
And our site is still running fine.

I am wondering if this is a wp-config.php problem, .htaccess or some other file that is not overwritten when I downgrade to resolve the problem????