I am using Joomla 1.5.17 and JoomSEF 3.6.2

My site is www.uschallengecoins.com and on the homepage I get this error at the bottom Fatal error: Call to undefined function BuildRoute() in /home/uscc/public_html/components/com_sef/joomsef.php on line 245

I have no idea what is causing this and I am starting to stress a bit here. Anyone have any ideas? Thanks

Adam