Widget.php – Problem with dashboard display

I am having a problem with the Appearance>Widget command on my Dashboard. When I open that page it looks nothing like the page should look. I get a single column with each widget on a seperate row, followed by each column in a row. It doesn’t allow drag and drop. Has anyone else seen this. It worked last night, just suddenly stopped working today. Will it help to copy another widget.php file into the WPIncludes folder? Help!