Sitecore 7.x and Internet Explorer 11 and Content Item Fields get covered in Grey Box

Here are the steps to reproduce:

1) Open Internet Explorer 11.
2) Log into the Sitecore Admin selecting Content Editor.
3) Click on a node in the tree.
4) On the right hand side move the mouse around, especially over the edit html for a rich text field.  The whole field panel will turn grey.
5) Click on a node in the tree and the grey will disappear and fields will come back.

WORKAROUND: Open windows explorer and edit \sitecore\shell\Themes\Standard\Default\content manager.css

The editorFrame style has the following:

#EditorFrames {

  width: 100%;

  position: absolute;

  top: 0;

  bottom: 0;

  margin-top: 25px;

  background: white;

}

In IE 11 this will width:100% will not work properly.  Change this style to:

#EditorFrames {

  width: 100%;

  position: absolute;

  top: 0;

  bottom: 0;

  margin-top: 25px;

  background: white;
min-width:400px;
min-height:1000px

}

This will resolve the issue however since this is a Sitecore file you have to be careful during upgrades that this fix is not overwritten.