Internet Explorer access - Run Time Error!

Why is it that when I log on under my user name and try to bring up Internet explorer while another family member is still logged on under their user name, I get " Run Time Error! Program: C:\Program Files\Internet Explorer\iexplore.exe" ?  I then have to go back and exit them from internet explorer and sometimes log them out altogether.  This just started recently.  I have a Dimension 4700 using Windows XP.