Critical Error WordPress site

My website (hunterbabydotcomdotau) is down and I can't access the back end with my login - it doesn't recognise my password which is correct and when I try to reset it it says 'invalid'. My webpages has the following script in the header: [14-May-2012 23:53:38] PHP Fatal error: Call to undefined function get_option() in /home/hunterba/public_html/wp-content/plugins/gold_cart_files_plugin/merchants/[login to view URL] on line 10 [14-May-2012 23:57:02] PHP Fatal error: Call to undefined function get_option() in /home/hunterba/public_html/wp-content/plugins/gold_cart_files_plugin/merchants/[login to view URL] on line 38 [14-May-2012 23:57:11] PHP Fatal error: Call to undefined function get_option() in /home/hunterba/public_html/wp-content/plugins/gold_cart_files_plugin/merchants/[login to view URL] on line 10 I need to resolve this asap!