OK, as I've now established, and hopefully so have you, in another topic ("Every file is corrupt?") this IS a conspiracy and we're being messed around by "T3 or Higher" connections all (or at least nearly all) or which have dud files to make us sad.

What I've discovered, in the 5 minutes since identifying the problem, as a good answer to this is, every time you do a search get the list of results to compile according to speed, "T3 or higher" at the top of the list. Then work your way down and, using a Mac on OSX (I'm sure there's an equivalent on PC's) control click each highly rated result and select "Block Host".

Do this a couple of times and all those nasty corrupt file harbouring entities simply disappear from your search result listings.

Bliss!