In Unity onieric when using dashboard to open a folder or place or if you click on an external drive on the dock, banshee always opens. . Banshee works fine when it is needed, but has taken over nautilus when a nautilus folder is called upon in the dash. Clicking "Files" folder on the dock opens nautilus fine.
This showed up after an upgrade through software channel from 11.04 to Onieric
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: unity 4.24.0-0ubuntu2b1
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: i386
CompizPlugins: [core,bailer,detection,composite,opengl,decor,resize,compiztoolbox,imgsvg,grid,move,imgpng,mousepoll,unitymtgrabhandles,regex,vpswitch,gnomecompat,snap,place,session,animation,workarounds,wall,expo,fade,ezoom,scale,switcher,unityshell]
Date: Thu Nov 17 14:25:48 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
ProcEnviron:
LANGUAGE=en_CA:en
PATH=(custom, no user)
LANG=en_CA.UTF-8
SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: Upgraded to oneiric on 2011-10-21 (27 days ago)
not really sure what could be the cause here though I have seen a couple of other such bug reports in the past.