Steps to reproduce:
Open Internet Explorer
Navigate to http://serverfault.com (and possibly any other SE site)
Create a comment
Edit that comment
Finalize the edit by using the Enter/Return key. Do not click the "Save Edit" button.
This causes the focus to be "trapped" in some way and mouse functions, including scroll wheel, do not work until the page is refreshed. When this happens, a blinking cursor appears after the edit link, as pictured below.