Hi guys!
I've found a bug, fully described here http://forum.virtuemart.net/index.php?topic=112582.msg421460#msg421460 (http://forum.virtuemart.net/index.php?topic=112582.msg421460#msg421460), with a solution.
Fancybox is included incorrectly, since the whole check for Fancybox state is missing, IMHO.
This spoils things up, leading to possible JS conflicts.