Bought the Virtuemart extension for JoomnSEF, but when I install it, the whole site crashes with this error:

Warning: extract() [function.extract]: First argument should be an array in /home/firesafe/public_html/components/com_sef/sef_ext/com_virtuemart.php on line 17

Fatal error: Cannot instantiate non-existent class: sefext_com_virtuemart in /home/firesafe/public_html/components/com_sef/joomsef.php on line 742

??

Thanks, Paul.