Error processing request after upgrading to 1.9. Please help. :(

[Smacks1879]

There has been an error processing your request

Here is my site.  https://www.cheapfishinggear.com

Invalid method WP_CustomMenu_Block_Topmenu::showHomeLink(Array
(
)
)

Trace:
#0 /home/cheapfis/public_html/app/design/frontend/ultimo/default/template/webandpeople/custommenu/top.phtml(8): Varien_Object->__call('showHomeLink', Array)
#1 /home/cheapfis/public_html/app/design/frontend/ultimo/default/template/webandpeople/custommenu/top.phtml(8): WP_CustomMenu_Block_Topmenu->showHomeLink()
#2 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/home/cheapfis/...')
#3 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/ultimo...')
#4 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#5 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#6 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
#7 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Text_List->_toHtml()
#8 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(637): Mage_Core_Block_Abstract->toHtml()
#9 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(581): Mage_Core_Block_Abstract->_getChildHtml('topMenu', true)
#10 /home/cheapfis/public_html/app/design/frontend/ultimo/default/template/page/html/header.phtml(345): Mage_Core_Block_Abstract->getChildHtml('topMenu')
#11 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/home/cheapfis/...')
#12 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/ultimo...')
#13 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#14 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#15 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(637): Mage_Core_Block_Abstract->toHtml()
#16 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(581): Mage_Core_Block_Abstract->_getChildHtml('header', true)
#17 /home/cheapfis/public_html/app/design/frontend/ultimo/default/template/page/1column.phtml(87): Mage_Core_Block_Abstract->getChildHtml('header')
#18 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(241): include('/home/cheapfis/...')
#19 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/ultimo...')
#20 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#21 /home/cheapfis/public_html/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#22 /home/cheapfis/public_html/app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
#23 /home/cheapfis/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
#24 /home/cheapfis/public_html/app/code/core/Mage/Cms/Helper/Page.php(137): Mage_Core_Controller_Varien_Action->renderLayout()
#25 /home/cheapfis/public_html/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'home')
#26 /home/cheapfis/public_html/app/code/core/Mage/Cms/controllers/IndexController.php(45): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'home')
#27 /home/cheapfis/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Cms_IndexController->indexAction()
#28 /home/cheapfis/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index')
#29 /home/cheapfis/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#30 /home/cheapfis/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#31 /home/cheapfis/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#32 /home/cheapfis/public_html/index.php(83): Mage::run('', 'store')
#33 {main}

[horobeanu]

First of all is a BAD idea to do an upgrade on PRODUCTION.

Before doing a Magento upgrade please read this: devdocs.magento.com/guides/m1x/install/installing_upgrade_details.html

Because you are on PRODUCTION environment I recommend to activate maintenance mode than resolve upgrade problems.

[chiefair]

Contact the people who created this => WP CustomMenu

Modules and themes created for Magento before 1.9.2.x will usually fall flat on their face when you upgrade. The developers know this and have likely had to upgrade their product to work with it, contact them.

No information given, but you probably upgraded from 1.8 or previous to 1.9 without using a dev environment to test this out, so are paying the price for free software and free support by losing your income stream.