IE8 back button stop working after a while.   This is a problem caused by different factors, but one major cause is the individual add-on to the browser.

To quicky resolve this, you would go to Task Manager and select “Processes” tab, look through the list and you will notice multiple instance of  iexplore32.exe are running.  Simply select each iexplore32.exe, and then “End Process”.

Re-launch your IE, the problem should be fixed.