can't select flash Rated 4 out of 5 stars
flash is still a big issue to adblock or this helper... eg. http://www.freewareppc.com/This review is for a previous version of the add-on (1.0.2).
Not something this extension can change
That's just how it is - plugins like Flash aren't like all the other elements of the web page. In particular, the browser doesn't get notified when the mouse moves over a plugin, meaning that the selection in Element Hiding Helper won't change either.
Not that I see any good reason to use Element Hiding Helper on Flash - you want to block Flash, not hide it. So open blockable items list and look for objects (see Adblock Plus FAQ for details).