My bitcoint-qt client is crashing due to insufficient file descriptors repeatedly even after I set the ulimits to 65535
and the answer is....

if you use a shared folder on a VM the linux open file desc spec is irrelevant.
So I created a diskimage directly mounted in the host...
and voilà problem solved by avoiding the vbox host shared folder service indirection.
maybe playing with the vbox host config and system config would have helped as well.....