Magento empty blank product page - magento

Question

I got some problems with my magento store. The product page view is empty.
I've debugged it and in the exception log I got this message:
2014-02-18T21:45:34+00:00 ERR (3):
exception 'Mage_Core_Exception' with message 'Method "addJqueryLibrary" is not defined in "Magentothem_Upsellslider_Model_Layout_Generate_Observer"' in /home/mellimello/public_html/app/Mage.php:595
Stack trace:
#0 /home/mellimello/public_html/app/code/core/Mage/Core/Model/App.php(1340): Mage::throwException('Method "addJque...')
#1 /home/mellimello/public_html/app/code/core/Mage/Core/Model/App.php(1317): Mage_Core_Model_App->_callObserverMethod(Object(Magentothem_Upsellslider_Model_Layout_Generate_Observer), 'addJqueryLibrar...', Object(Varien_Event_Observer))
#2 /home/mellimello/public_html/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#3 /home/mellimello/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(351): Mage::dispatchEvent('controller_acti...', Array)
#4 /home/mellimello/public_html/app/code/core/Mage/Catalog/Helper/Product/View.php(73): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#5 /home/mellimello/public_html/app/code/core/Mage/Catalog/Helper/Product/View.php(144): Mage_Catalog_Helper_Product_View->initProductLayout(Object(Mage_Catalog_Model_Product), Object(Mage_Catalog_ProductController))
#6 /home/mellimello/public_html/app/code/core/Mage/Catalog/controllers/ProductController.php(132): Mage_Catalog_Helper_Product_View->prepareAndRender(6, Object(Mage_Catalog_ProductController), Object(Varien_Object))
#7 /home/mellimello/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Catalog_ProductController->viewAction()
#8 /home/mellimello/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch('view')
#9 /home/mellimello/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))
#10 /home/mellimello/public_html/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#11 /home/mellimello/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#12 /home/mellimello/public_html/index.php(87): Mage::run('', 'store')
#13 {main}

Answer 1

It looks like the module Magentothem Upsellslider is broken. If you installed the module from somewhere else, contact the creator and tell them it isn't working. In the meantime, uninstall it by removing the file app/code/etc/modules/Magentothem_Upsellslider.xml and clear your cache.
If this is your module, you seem to be trying to call a non-existent function addJqueryLibrary in your observer. Perhaps you have a typo... should it be addJQueryLibrary?