When i enable cache in the admin of our Magento (a new extensions requires us to do this), the store goes down and gives the following error on page load.
Warning: simplexml_load_string() [function.simplexml-load-string]: Entity: line 51: parser error : StartTag: invalid element name in /home/sitename/public_html/lib/Varien/Simplexml/Config.php on line 383
#0 [internal function]: mageCoreErrorHandler(2, 'simplexml_load_...', '/home/sitename...', 383, Array)
#1 /home/sitename/public_html/lib/Varien/Simplexml/Config.php(383): simplexml_load_string('loadCache()
#3 /home/sitename/public_html/app/code/core/Mage/Core/Model/App.php(408): Mage_Core_Model_Config->loadModulesCache()
#4 /home/sitename/public_html/app/code/core/Mage/Core/Model/App.php(338): Mage_Core_Model_App->_initModules()
#5 /home/sitename/public_html/app/Mage.php(640): Mage_Core_Model_App->run(Array)
#6 /home/sitename/public_html/index.php(80): Mage::run('', 'store')
#7 {main}
We cannot load the store anymore.
Most probably this issue comes when the XML file (config.xml or {layout}.xml) having the XML syntax error. So please check your new extension's xml files properly. You can check the xml file syntax by opening the file in any browser.
Hope this will help.