10.7 and up have a little feature called elastic scrolling. When you get to the top of a page and you keep scrolling you see the linen background. There is a NAS devices whose web portals seems to be pretty shady overall, but specifically seems to lock up when this rubber band effect kicks in. So to disable:
defaults write -g NSScrollViewRubberbanding -bool FALSE
To disable the disable, or re-enable the effect:
defaults write -g NSScrollViewRubberbanding -bool TRUE
