I had this mystery crash yesterday. It looks vaguely like https://bugzilla.gnome.org/show_bug.cgi?id=638257

Broken Mono?

Mono JIT compiler version 2.6.7 (Debian 2.6.7-4)
Copyright (C) 2002-2010 Novell, Inc and Contributors. www.mono-project.com
	TLS:           __thread
	GC:            Included Boehm (with typed GC and Parallel Mark)
	SIGSEGV:       altstack
	Notifications: epoll
	Architecture:  amd64
	Disabled:      none


[438 Debug 03:29:39.228] (libbanshee:player) [Gapless] Requesting next track
System.String doesn't implement interface Banshee.Collection.Database.IFilterListModel
**
ERROR:mini-trampolines.c:183:mono_convert_imt_slot_to_vtable_slot: code should not be reached
Stacktrace:

  at Banshee.Collection.Database.DatabaseTrackListModel.Reload (Hyena.Data.IListModel) [0x00211] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Collection.Database/DatabaseTrackListModel.cs:319
  at Banshee.Collection.Database.DatabaseTrackListModel.Reload (Hyena.Data.IListModel) [0x00100] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Collection.Database/DatabaseTrackListModel.cs:287
  at Banshee.Collection.Database.DatabaseTrackListModel.Reload () [0x00000] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Collection.Database/DatabaseTrackListModel.cs:255
  at Banshee.Sources.DatabaseSource.RateLimitedReload () [0x0000d] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Sources/DatabaseSource.cs:412
  at Banshee.Base.RateLimiter.InnerExecute () [0x0001b] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Base/RateLimiter.cs:64
  at Banshee.Base.RateLimiter.Execute () [0x00036] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Base/RateLimiter.cs:55
  at Banshee.Sources.DatabaseSource.Reload () [0x00010] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Sources/DatabaseSource.cs:406
  at Banshee.SmartPlaylist.SmartPlaylistSource.Reload () [0x0002c] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs:387
  at Banshee.SmartPlaylist.SmartPlaylistSource.RefreshAndReload () [0x00006] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs:374
  at Banshee.SmartPlaylist.SmartPlaylistSource.HandleTracksChanged (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) [0x00027] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs:488
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00044, 0x0005e>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at (wrapper delegate-invoke) Banshee.Sources.PrimarySource/TrackEventHandler.invoke_void__this___Source_TrackEventArgs (Banshee.Sources.Source,Banshee.Sources.TrackEventArgs) <IL 0x00059, 0x00098>
  at Banshee.Sources.PrimarySource/<OnTracksChanged>c__AnonStorey20.<>m__17 () [0x0004d] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Sources/PrimarySource.cs:409
  at Hyena.ThreadAssist.SpawnFromMain (System.Threading.ThreadStart) [0x00017] in /home/david/Projekter/banshee/src/Hyena/Hyena/Hyena/ThreadAssist.cs:112
  at Banshee.Sources.PrimarySource.OnTracksChanged (Hyena.Query.QueryField[]) [0x00014] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Sources/PrimarySource.cs:398
  at Banshee.Sources.PrimarySource.NotifyTracksChanged (Hyena.Query.QueryField[]) [0x00000] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Sources/PrimarySource.cs:335
  at Banshee.Collection.Database.DatabaseTrackInfo.Save (bool,Hyena.Query.QueryField[]) [0x0010c] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Collection.Database/DatabaseTrackInfo.cs:221
  at Banshee.Collection.Database.DatabaseTrackInfo.UpdateLastPlayed () [0x0000c] in /home/david/Projekter/banshee/src/Core/Banshee.Services/Banshee.Collection.Database/DatabaseTrackInfo.cs:182
  at Banshee.GStreamer.PlayerEngine.OnAboutToFinish (intptr) [0x00000] in /home/david/Projekter/banshee/src/Backends/Banshee.GStreamer/Banshee.GStreamer/PlayerEngine.cs:368
  at (wrapper native-to-managed) Banshee.GStreamer.PlayerEngine.OnAboutToFinish (intptr) <IL 0x00022, 0x0006f>

Native stacktrace:

	banshee-1() [0x4890b1]
	/lib/libpthread.so.0(+0xfd70) [0x7f759edd0d70]
	/lib/libc.so.6(gsignal+0x35) [0x7f759e7edba5]
	/lib/libc.so.6(abort+0x186) [0x7f759e7f14f6]
	/lib/libglib-2.0.so.0(+0x687dd) [0x7f759f4547dd]
	banshee-1() [0x489876]
	banshee-1() [0x48a481]
	[0x40c72168]

Debug info from gdb:

Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operationen er ikke tilladt.

=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.
=================================================================

Afbrudt (SIGABRT)