Audioscrobbling silently failing (and MusicBrainz ID)

Hi, I'm having some trouble getting the AudioScrobbling support in 3.0 working.
My subsonic.log shows plenty of entries "Successfully scrobbled song 'Son of a Preacher Man' for user haraldme at Last.fm.", and network packet sniffing appears to confirm that the AudioScrobbler submission POST was successful -- yet still my last.fm page keeps saying "No recent track to display."
My first guess for the cause of this is that my tracks appear to be submitted to AudioScrobbler with zero track length (l[0]=0). Could this be an artifact of my setup doing transcoding from FLAC to Ogg Vorbis (e.g. maybe the track length isn't known until the entire stream has been played)? If so, wouldn't it be better to submit with "l[0]=", i.e. to tell that Subsonic doesn't know the track's length?
If the zero size isn't the problem, my second guess would be that this is caused by some kind of protocol violation from Subsonic's side, e.g. as detailed in the protocol spec:
I also noticed that the POST data produced by Subsonic doesn't include any MusicBrainz ID even though my FLAC-to-Ogg-transcoded streams do include proper MUSICBRAINZ_TRACKID comments. Is support for AudioScrobbling MusizBrainz IDs planned?
BTW, I'm running this on an Ubuntu Linux 7.04 Beta box, under Sun Java 5; both Java and Tomcat 5.5 installed from Ubuntu packages. Let me know if you'd like to have a look at the packet sniffing data or my FLAC/Ogg tags/comments.
My subsonic.log shows plenty of entries "Successfully scrobbled song 'Son of a Preacher Man' for user haraldme at Last.fm.", and network packet sniffing appears to confirm that the AudioScrobbler submission POST was successful -- yet still my last.fm page keeps saying "No recent track to display."

My first guess for the cause of this is that my tracks appear to be submitted to AudioScrobbler with zero track length (l[0]=0). Could this be an artifact of my setup doing transcoding from FLAC to Ogg Vorbis (e.g. maybe the track length isn't known until the entire stream has been played)? If so, wouldn't it be better to submit with "l[0]=", i.e. to tell that Subsonic doesn't know the track's length?
If the zero size isn't the problem, my second guess would be that this is caused by some kind of protocol violation from Subsonic's side, e.g. as detailed in the protocol spec:
The three main reasons that submissions are OK'd but not entered are:
* Bad UTF-8
* Bad tagging (we now completely drop any entries which look crap, e.g. 01-artist_blah)
* Spam filter (sanity checks like claiming to have played 10 songs in 10 seconds -- not possible)
I also noticed that the POST data produced by Subsonic doesn't include any MusicBrainz ID even though my FLAC-to-Ogg-transcoded streams do include proper MUSICBRAINZ_TRACKID comments. Is support for AudioScrobbling MusizBrainz IDs planned?
BTW, I'm running this on an Ubuntu Linux 7.04 Beta box, under Sun Java 5; both Java and Tomcat 5.5 installed from Ubuntu packages. Let me know if you'd like to have a look at the packet sniffing data or my FLAC/Ogg tags/comments.