i haven't gdk-sharp installed. At synaptics there is no package with that
name!
Sorry I wasn't clearer, the libgtk2.0-cil package provides the gdk-sharp assembly used by Banshee. So that's to be expected.
libgtk2.0-cil » version: 2.12.1-1 is installed.
It sounds like you have the correct packages installed. Can you try another Mono-based application, e.g. Tomboy, F-Spot, GNOME Do, or even the legacy branch (i.e. 0.13.x or before) of Banshee? That would help determine if it's a problem with the Banshee package or something with Mono or whatnot.
Cheers,
Andrew