Audacious

You're playing tracks without having associated the plugin with a last.fm account, is that it?

Can you show the title of a track where that happens?

OK, I think I got it: did you set a track playing and then select another one while the first was still playing, without pausing or stopping it?
If so, I was able to reproduce this on my machine. Audacious doesn't call the "ended" or "stopped" hooks on such cases. I can workaround this but maybe the core should be calling one of those hooks.

1. Play track A;
2. Without pressing pause or stop, play track B;
3. When the track reaches a "scrobbable" state (i.e., half of it has played or 4 minutes have passed, whichever comes first), Audacious segfaults.

This happens because on step 2 the plugin didn't receive an "end" or "stop" signal.