tomboy 1.6.1 no longer works

[KB N]

Greetings,
After recent port tree and package updates (png related hugg updates), tomboy on my FreeBSD 9.0-STABLE no longer works. When I start it, I got the following errors. Any help would be appreciated.
Bong
$ tomboyMissing method System.Type::op_Equality(Type,Type) in assembly /usr/local/lib/mono/2.0/mscorlib.dll, referenced in assembly /usr/local/lib/mono/gac/gnome-sharp/2.24.0.0__35e10195dab3c99f/gnome-sharp.dll
Unhandled Exception: System.MissingMethodException: Method not found: 'System.Type.op_Equality'.  at Tomboy.GnomeApplication.Initialize (System.String locale_dir, System.String display_name, System.String process_name, System.String[] args) [0x00000] in <filename unknown>:0   at Tomboy.Application.Initialize (System.String locale_dir, System.String display_name, System.String process_name, System.String[] args) [0x00000] in <filename unknown>:0   at Tomboy.Tomboy.Main (System.String[] args) [0x00000] in <filename unknown>:0 [ERROR] FATAL UNHANDLED EXCEPTION: System.MissingMethodException: Method not found: 'System.Type.op_Equality'.  at Tomboy.GnomeApplication.Initialize (System.String locale_dir, System.String display_name, System.String process_name, System.String[] args) [0x00000] in <filename unknown>:0   at Tomboy.Application.Initialize (System.String locale_dir, System.String display_name, System.String process_name, System.String[] args) [0x00000] in <filename unknown>:0   at Tomboy.Tomboy.Main (System.String[] args) [0x00000] in <filename unknown>:0