Hmm, well I don't know what is going on with the search feature. To be frank, I think due to the changes IF is going under it might not be back..
As far as downloading IF videos is concerned, then all you need is real player:
http://uk.real.com/player/more
Download by clicking on "Free download" and install it. Once it is installed restart the browser. When you go in IF's video section, an icon on the top right hand corner will appear saying "download this video."
You simply click that and download. Example:
I hope that anwsers your Q(s).
Magnificent.