Upgrading mono to 1.1.17.1-5 (testing) was sufficient. Now tomboy runs normally.
$ dpkg -l '*mono*' | grep ^ii ii libmono-cairo1.0-cil 1.1.17.1-5 Mono Cairo library ii libmono-corlib1.0-cil 1.1.17.1-5 Mono core library (1.0) ii libmono-data-tds1.0-cil 1.1.17.1-5 Mono Data library ii libmono-peapi1.0-cil 1.1.17.1-5 Mono PEAPI library ii libmono-relaxng1.0-cil 1.1.17.1-5 Mono Relaxng library ii libmono-security1.0-cil 1.1.17.1-5 Mono Security library ii libmono-sharpzip0.84-cil 1.1.17.1-5 Mono SharpZipLib library ii libmono-system-data1.0-cil 1.1.17.1-5 Mono System.Data library ii libmono-system-runtime1.0-cil 1.1.17.1-5 Mono System.Runtime library ii libmono-system-web1.0-cil 1.1.17.1-5 Mono System.Web library ii libmono-system1.0-cil 1.1.17.1-5 Mono System libraries (1.0) ii libmono0 1.1.17.1-5 libraries for the Mono JIT ii libmono1.0-cil 1.1.17.1-5 Mono libraries (1.0) ii mono-common 1.1.17.1-5 common files for Mono ii mono-gac 1.1.17.1-5 Mono GAC tool ii mono-jit 1.1.17.1-5 fast CLI JIT/AOT compiler for Mono ii mono-mcs 1.1.17.1-5 Mono C# compiler ii mono-runtime 1.1.17.1-5 Mono runtime ii mono-utils 1.1.17.1-5 Mono utilities It seems that this bug also duplicates #388286 (crash of f-spot on start), currently assigned to libdbus-1-cil. However, in my case I did not remove libdbus-1-2. Mono upgrade was sufficient: $ dpkg -l 'libdbus-*' | grep ^ii ii libdbus-1-2 0.62-4 simple interprocess messaging system ii libdbus-1-3 0.93-1 simple interprocess messaging system ii libdbus-1-cil 0.63.git.20060719-4 CLI binding for D-BUS interprocess messaging ii libdbus-glib-1-2 0.71-2 simple interprocess messaging system (GLib-b ii libdbus-qt-1-1c2 0.62.git.20060814-2 simple interprocess messaging system (Qt-bas -- jetxee <[EMAIL PROTECTED]> -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]