I'm not certain about Shift+F4, as that used to unspan table cells.
Perhaps you have a custom ACL script set to modify the keymappings? If you're certain the older version had this, you can use the preference
useepic43keymappings
to bring it back. The Help Center shows exactly what is different between that version and the current one:
http://support.ptc.com/cs/help/arbortext_hc/ae61_hc/index.jspx?id=help1590&action=show