not mounting /proc results in the following (indeed still failing, but no segfaults):

Setting up mono-2.0-gac (2.4.3+dfsg-1ubuntu2) ...
Setting up mono-gac (2.4.3+dfsg-1ubuntu2) ...
* Installing 6 assemblies from libart2.0-cil into Mono
E: installing Assembly /usr/lib/cli/art-sharp-2.0/art-sharp.dll failed
E: Installation of libart2.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 6 assemblies from libgconf2.0-cil into Mono
E: installing Assembly /usr/lib/cli/gconf-sharp-2.0/gconf-sharp.dll failed
E: Installation of libgconf2.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from libglade2.0-cil into Mono
E: installing Assembly /usr/lib/cli/glade-sharp-2.0/glade-sharp.dll failed
E: Installation of libglade2.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from libglib2.0-cil into Mono
E: installing Assembly /usr/lib/cli/glib-sharp-2.0/glib-sharp.dll failed
E: Installation of libglib2.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from libgmime2.4-cil into Mono
E: installing Assembly /usr/lib/cli/gmime-sharp-2.4/gmime-sharp.dll failed
E: Installation of libgmime2.4-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 6 assemblies from libgnome-vfs2.0-cil into Mono
E: installing Assembly /usr/lib/cli/gnome-vfs-sharp-2.0/gnome-vfs-sharp.dll failed
E: Installation of libgnome-vfs2.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 2 assemblies from libgnome2.24-cil into Mono
E: installing Assembly /usr/lib/cli/gnome-sharp-2.24/gnome-sharp.dll failed
E: Installation of libgnome2.24-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from libgnomepanel2.24-cil into Mono
E: installing Assembly /usr/lib/cli/gnome-panel-sharp-2.24/gnome-panel-sharp.dll failed
E: Installation of libgnomepanel2.24-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 5 assemblies from libgtk2.0-cil into Mono
E: installing Assembly /usr/lib/cli/gtk-sharp-2.0/gtk-sharp.dll failed
E: Installation of libgtk2.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from liblaunchpad-integration1.0-cil into Mono
E: installing Assembly /usr/lib/cli/launchpad-integration-sharp-1/launchpad-integration-sharp.dll failed
E: Installation of liblaunchpad-integration1.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 3 assemblies from libmono-addins-gui0.2-cil into Mono
E: installing Assembly /usr/lib/cli/Mono.Addins.Gui-0.2/Mono.Addins.Gui.dll failed
E: Installation of libmono-addins-gui0.2-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 7 assemblies from libmono-addins0.2-cil into Mono
E: installing Assembly /usr/lib/cli/Mono.Addins-0.2/Mono.Addins.dll failed
E: Installation of libmono-addins0.2-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from libndesk-dbus-glib1.0-cil into Mono
E: installing Assembly /usr/lib/cli/NDesk.DBus.GLib-1.0/NDesk.DBus.GLib.dll failed
E: Installation of libndesk-dbus-glib1.0-cil with /usr/share/cli-common/runtimes.d/mono failed
* Installing 1 assembly from libndesk-dbus1.0-cil into Mono
E: installing Assembly /usr/lib/cli/NDesk.DBus-1.0/NDesk.DBus.dll failed
E: Installation of libndesk-dbus1.0-cil with /usr/share/cli-common/runtimes.d/mono failed