It's working OK for me right at this moment, although in same cases it is taking quite a few seconds to pull in a backdrop.
I tried using the debug version and I clicked on about 20 artists that I had no backdrops for and it found pics for all of them. In the log, there were a few 404 entries for Fanart though and it seems it pulled the pic in from Last.FM instead, despite pics being available from Fanart (I manually checked).
I will continue testing this to see if it breaks again. Perhaps it's a time of day thing, based on server load. I dunno, but the issue was intermittent when I reported it too, so it seems like it's something to do with Fanart's server sometimes not responding and giving a 404.
@Pinky - Thanks for the reply. I'm 99% sure this has nothing to do with Virgin Media now, cos the sites where the pics are being pulled from are reachable at all times.
I will post back with more info later and the full log file if/when this issue rears its ugly head again.