Mouse scrolling just stops


Has anyone else noticed that as you are working on a document, that WP documents stop responding to mouse-controlled scrolling within the body of the document? The page up and down buttons on the keyboard also stop working. The scroll bar to the right of the screen still works, as do the page up and down double arrows in the bottom right corner of the screen.
This occurs after I have been working on the same document for a while. Usually shutting WP down and reopening it will cause this issue to disappear, at least until it reappears.
It is very annoying and has been happening for at least two if not three versions. I regularly delete temp files and run WPLook to check for file corruption so I don't think either are causing this problem.