The same thing is happening to me. The songs don't show up when they're playing, but they finally scrobble and show up in the recent tracks list like 10 minutes later. It's annoying cos I don't know whether they're actually scrobbling or not... Just now, the song I'm listening to right now showed up as 'scrobbling now' but it's almost finished lol, it's a bit slow.
Seems to be sort of working again for me but not fully songs I played 10 or 15 mins ago are now starting to show up on my Last FM page but songs I have just played in last few mins don't seem to show up still.
Last FM still seems a little show in shown up songs on my Last FM page.