error Model_Rewrite when work with Magento CMS?

error Model_Rewrite when work with Magento CMS?

I had worked at Magento eCommerce cms I had my website well and every
thing is well one of the pages is login page when I tried to login i had
error . I tried to know what this error mean but i couldn't . i hope if y
help me.
<pre>Item (Aitoc_Aitdownloadablefiles_Model_Rewrite_FrontCatalogProduct)
with the same id "197" already exist<br />
Trace:
#0
/home/elaraby/public_html/app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php(265):
Varien_Data_Collection-&gt;addItem(Object(Aitoc_Aitdownloadablefiles_Model_Rewrite_FrontCatalogProduct))
#1
/home/elaraby/public_html/app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php(1055):
Mage_Eav_Model_Entity_Collection_Abstract-&gt;addItem(Object(Aitoc_Aitdownloadablefiles_Model_Rewrite_FrontCatalogProduct))
#2
/home/elaraby/public_html/app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php(869):
Mage_Eav_Model_Entity_Collection_Abstract-&gt;_loadEntities(false, false)
#3
/home/elaraby/public_html/app/code/core/Mage/Catalog/Helper/Product/Compare.php(211):
Mage_Eav_Model_Entity_Collection_Abstract-&gt;load()
#4
/home/elaraby/public_html/app/design/frontend/base/default/template/catalog/product/compare/sidebar.phtml(30):
Mage_Catalog_Helper_Product_Compare-&gt;getItemCollection()
#5
/home/elaraby/public_html/var/ait_rewrite/67b58abff9e6bd7b400bb2fc1903bf2f.php(412):
include('/home/elaraby/p...')
#6
/home/elaraby/public_html/var/ait_rewrite/67b58abff9e6bd7b400bb2fc1903bf2f.php(274):
Mage_Core_Block_Template-&gt;fetchView('frontend/base/d...')
#7
/home/elaraby/public_html/var/ait_rewrite/67b58abff9e6bd7b400bb2fc1903bf2f.php(288):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Template-&gt;renderView()
#8
/home/elaraby/public_html/var/ait_rewrite/6bfe16ca572eea47db567910902c6209.php(865):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Template-&gt;_toHtml()
#9
/home/elaraby/public_html/app/code/core/Mage/Core/Block/Text/List.php(43):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Abstract-&gt;toHtml()
#10
/home/elaraby/public_html/var/ait_rewrite/6bfe16ca572eea47db567910902c6209.php(865):
Mage_Core_Block_Text_List-&gt;_toHtml()
#11
/home/elaraby/public_html/var/ait_rewrite/6bfe16ca572eea47db567910902c6209.php(584):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Abstract-&gt;toHtml()
#12
/home/elaraby/public_html/var/ait_rewrite/6bfe16ca572eea47db567910902c6209.php(528):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Abstract-&gt;_getChildHtml('left',
true)
#13
/home/elaraby/public_html/app/design/frontend/elaraby_group/theme321/template/page/2columns-left.phtml(53):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Abstract-&gt;getChildHtml('left')
#14
/home/elaraby/public_html/var/ait_rewrite/67b58abff9e6bd7b400bb2fc1903bf2f.php(412):
include('/home/elaraby/p...')
#15
/home/elaraby/public_html/var/ait_rewrite/67b58abff9e6bd7b400bb2fc1903bf2f.php(274):
Mage_Core_Block_Template-&gt;fetchView('frontend/elarab...')
#16
/home/elaraby/public_html/var/ait_rewrite/67b58abff9e6bd7b400bb2fc1903bf2f.php(288):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Template-&gt;renderView()
#17
/home/elaraby/public_html/var/ait_rewrite/6bfe16ca572eea47db567910902c6209.php(865):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Template-&gt;_toHtml()
#18
/home/elaraby/public_html/app/code/core/Mage/Core/Model/Layout.php(529):
Aitoc_Aitsys_Model_Rewriter_Mage_Core_Block_Abstract-&gt;toHtml()
#19
/home/elaraby/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(391):
Mage_Core_Model_Layout-&gt;getOutput()
#20
/home/elaraby/public_html/app/code/core/Mage/Customer/controllers/AccountController.php(115):
Mage_Core_Controller_Varien_Action-&gt;renderLayout()
#21
/home/elaraby/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(420):
Mage_Customer_AccountController-&gt;indexAction()
#22
/home/elaraby/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250):
Mage_Core_Controller_Varien_Action-&gt;dispatch('index')
#23
/home/elaraby/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(176):
Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
#24 /home/elaraby/public_html/app/code/core/Mage/Core/Model/App.php(349):
Mage_Core_Controller_Varien_Front-&gt;dispatch()
#25 /home/elaraby/public_html/app/Mage.php(640):
Mage_Core_Model_App-&gt;run(Array)
#26 /home/elaraby/public_html/index.php(80): Mage::run('', 'store')
#27 {main}<br />