are you sure it leaked from the block and not the fitting or clamp???
the manufacturer of the block told us they pressure test all the blocks... mhhh...
ive unmounted and mounted several blocks and i usually put too much pressure on things
so im surprised ive never seen this... and my block is perfectly fine, no paint cracks, nothing...
did your block have paint cracks from the start? or they developed later?

sounds like poor quality control from the maker of the blocks, sorry guys! :S
or could it be that they use a bad solder that slowly dissapears in water?
or maybe foxconn should pressure test the blocks when they are mounted on the board, since screwing the block onto the heatpipe array could put pressure on the block? but... not really, the screws put pressure on the base plate, and there is no pressure on the block cover at all when mounting it hmmm...