Hello,
I not sure, if this was already reported, but
1) You should upgrade jquery.fancybox-1.3.4.*js, or, at least, replace "e.browser.msie" by "navigator.userAgent.match(/msie/i)" (taken from newer Fancybox)
2) You should modify "components\com_virtuemart\views\category\view.html.php" by adding new line "$category->event = new stdClass();" before line 187 (before first usage of "$category->event->") to avoid warnings... with older PHP this class got created automatically, but now...)
BR,
Shinigami