SEF Advance 1.6.5 and virtuemart 1.1.2

I am just working on developing my site onto J 1.5,

I have purchased SEF Advance 2008 and installed along with the sef_ext for virtuemart.

Now when i try to click on a link to open the virtuemart catalogue i get the following error.

Fatal error: Call to a member function setQuery() on a non-object in /home/mydomain/public_html/2009/components/com_virtuemart/sef_ext.php on line 268

Any ideas? 

Mark

Legacy mode plugin must be activated on Joomla 1.5.
I look into minimizing the work in extension maintenance so I don't release a separate native extension for 1.5.