just curious what is the version of your firmware (below 2.06?)
why?...i notified same issue when i use uTorrent (ping flooding attack) when i have installed 2.05 (and bellow), i guess dir600 wrongly detect as ping flooding traffic from uTorrent (download on computer was ok).
Later i installed 2.06 (not because of above mentioned reason), looking in tab "Status" i never seen "Ping floding attack"...i presume D-link "fixed" (one of) bugs....?!