So one thing I have noticed over the past couple submissions is that for some reason in my case when I update my last.fm profile with songs I have listened to through rockbox, even songs I have skipped over only letting play a few seconds tops are getting posted as if I had listened to them completely. Often this means I have hundreds posted in the span of only actually listening to a few dozen or so.
So far I have used
http://scrob.paulstead.com/ to do the uploading as it looks the most feature complete and web based. I don't have anything to go on currently but I will try and post a log file snippet next time I go to update.