My home music-playing setup consists of a Linux box running MPD, a client-server music playing system. To this, the mpdscribble client is attached, monitoring its status and sending the details of tracks played to last.fm. As of a few days ago, though, mpdscribble stopped working; it connects to last.fm's servers well enough, though once the time comes to send a track, it reports an authentication error, as if the password were incorrect.
I have tried the same username and password combination for logging into the website, and for using the official OSX last.fm client, and it works. I have also tried two other, independent, MPD/last.fm clients (scmpc and lastfmsubmitd), and found that they had the same problem; as, indeed, does the (somewhat old) third-party iScrobbler client for OSX. (This was, needless to say, on two different machines.)
Could last.fm have broken an older version of the AudioScrobbler protocol used by a lot of open-source software? (It appears that these clients use protocol 1.1, whereas there is now a 1.2 protocol.) Oddly enough, a Google search fails to reveal anybody else reporting this problem.
Apparently a workaround is to change your password (to the same one as before will work). Which suggests that this issue has to do with localised data corruption on the last.fm submission servers.
Yeah, I"m having the exact same problem