I was trying to fix it in CSS menu and Mega menu
(Unfortunately without success)
The problem with IE-7 . the sub menu start to open from the wrong point of the <li> father.
* I add PrtScn from IE-7 (With the problem) And
IE-8 (without the problem)

?
/*
#------------------------------------------------------------------------
# Party freak - March 2010 (for Joomla 1.5)
#
# Copyright (C) 2007-2010 Gavick.com. All Rights Reserved.
# License: Copyrighted Commercial Software
# Website: http://www.gavick.com
# Support: [email protected]
#------------------------------------------------------------------------
# Based on T3 Framework
#------------------------------------------------------------------------
# Copyright (C) 2004-2009 J.O.O.M Solutions Co., Ltd. All Rights Reserved.
# @license - GNU/GPL, http://www.gnu.org/copyleft/gpl.html
# Author: J.O.O.M Solutions Co., Ltd
# Websites: http://www.joomlart.com - http://www.joomlancers.com
#------------------------------------------------------------------------
*/
/* Son of Suckerfish Dropdowns
---------------------------------------------------------
Originally developed by Patrick Griffiths and Dan Webb
http://www.htmldog.com/articles/suckerfish/dropdowns/
---------------------------------------------------------*/
#gk-cssmenu { margin: 0; /* all lists */ padding: 0; float: right; direction:ltr; }
#gk-cssmenu ul { margin: 0; /* all lists */ padding: 0; position:relative;}
#gk-cssmenu li { float: right; /* all list items */ display: block; cursor: pointer; direction:rtl; width:auto; position:relative; zoom:1; }
#gk-cssmenu li ul { width: 14.9em; position: absolute; /* second-level lists */ z-index: 99; top:-999em; right:0; /* using left instead of display to hide menus because display: none isn't read by screen readers */ height: auto; }
#gk-cssmenu li ul ul { margin: -25px 14.9em 0 0; /* third-and-above-level lists */ }
#gk-cssmenu li li { padding: 0; margin: 0; width: 14.9em; position:static;}
#gk-cssmenu li:hover ul ul,
#gk-cssmenu li:hover ul ul ul,
#gk-cssmenu li.sfhover ul ul,
#gk-cssmenu li.havechildsfhover ul ul,
#gk-cssmenu li.havechild-activesfhover ul ul,
#gk-cssmenu li.activesfhover ul ul,
#gk-cssmenu li.sfhover ul ul ul,
#gk-cssmenu li.havechildsfhover ul ul ul,
#gk-cssmenu li.havechild-activesfhover ul ul ul,
#gk-cssmenu li.activesfhover ul ul ul { top:-999em; right:0; }
/* This "unhides" the sub-menus (left: -999em is what hides them) */
#gk-cssmenu li:hover ul,
#gk-cssmenu li li:hover ul,
#gk-cssmenu li li li:hover ul,
#gk-cssmenu li.sfhover ul,
#gk-cssmenu li.havechildsfhover ul,
#gk-cssmenu li.havechild-activesfhover ul,
#gk-cssmenu li.activesfhover ul,
#gk-cssmenu li li.sfhover ul,
#gk-cssmenu li li.havesubchildsfhover ul,
#gk-cssmenu li li.havesubchild-activesfhover ul,
#gk-cssmenu li li.activesfhover ul,
#gk-cssmenu li li li.sfhover ul,
#gk-cssmenu li li li.havesubchildsfhover ul,
#gk-cssmenu li li li.havesubchild-activesfhover ul,
#gk-cssmenu li li li.activesfhover ul { top:auto; right:0;}
/* STYLING THE MENU
-----------------------------------*/
/* 1st level */
#gk-cssmenu li a { display: block; text-decoration: none; }
/* 2nd level and above */
#gk-cssmenu li ul { border-top: 0;}
#gk-cssmenu li ul li { background: none; }
#gk-cssmenu li ul a { border-right: 0; border-left: 0; margin: 0; background: none; font-weight: normal; line-height: normal; }
#gk-cssmenu .menu-desc{display:none!important;}