I am able to mount my android galaxy nexus phone with mtpfs.  Everything has been set up fine.

I'm using the latest libmtp release (1.1.2) and the latest svn trunk of mtpfs, as older versions of both of these didn't work.

I have in the root of my phone (mounted on /media/mtp with a fuse entry in fstab) a .is_audio_player file.  I have tried it with both a blank version and a completed version:

name=GalaxyNexus
audio_folders=Music/
output_formats=application/ogg
cover_art_file_type=jpeg
cover_art_file_name=AlbumArt.jpg
cover_art_size=640
playlist_format=audio/x-scpls,audio/x-mpegurl
playlist_path=Music/Playlist/

I get the same error either way.  Banshee says "ignoring unmounted volume mtp" when I leave mtp unmounted, and doesn't do anything, so I assume I have to have mtp already mounted.  If I'm wrong, well, it doesn't work either way.

Mounted, i get the following error message:

[Warn  19:03:10.751] Caught an exception - System.ArgumentNullException: Argument cannot be null. (in `mscorlib')
  at System.Int32.Parse (System.String s, NumberStyles style, IFormatProvider provider) [0x00000] in <filename unknown>:0 
  at System.Int32.Parse (System.String s, NumberStyles style) [0x00000] in <filename unknown>:0 
  at Banshee.Hardware.Gio.UsbDevice.GetVendorId (IUsbDevice device) [0x00000] in <filename unknown>:0 
  at Banshee.Hardware.Gio.UsbDevice.get_VendorId () [0x00000] in <filename unknown>:0 
  at Banshee.Dap.MassStorage.DeviceMapper.Map (Banshee.Dap.MassStorage.MassStorageSource source) [0x00000] in <filename unknown>:0 
  at Banshee.Dap.MassStorage.MassStorageSource.DeviceInitialize (IDevice device) [0x00000] in <filename unknown>:0 
  at Banshee.Dap.DapService.FindDeviceSource (IDevice device) [0x00000] in <filename unknown>:0 

I can confirm that this only happens when I have mtp (on /media/mtp, 777 root root) mounted, so I suppose it's trying to read something from the device.

If I'm misunderstanding and Banshee has its own method for dealing with MTP devices that for some reason isn't working (both with and without an entry in fstab and with and without the volume mounted), I'm not sure what I should be doing.

I've looked on google and it seems to work fine for everyone else as soon as they add the .is_audio_player file, but even with the file it still isn't recognized.