although i dont quite like how the blue liquid looks in there, i think thats how its supposed to be...take a look here
http://www.xtremesystems.org/forums/...xspc+gpu+block
or XSPC site
http://www.xspc.biz/razor9600gt.php
it appears that the "forgotten" o-ring is just not a part of the block..
i doubt emailing xspc would yield any results but you could try...otherwise you could modify the acrylic to fit one oring yourself