"FATAL UNHANDLED EXCEPTION" after upgrading to Ubuntu 11.10

[Mario César Señoranis]

After upgrading to Ubuntu 11.10 Oneiric. Couturier fails to start.

$ /usr/bin/mono /usr/lib/couturier/Couturier.exe
Missing method System.Type::op_Inequality(Type,Type) in assembly /usr/lib/mono/2.0/mscorlib.dll, referenced in assembly /usr/lib/mono/gac/gtk-sharp/2.12.0.0__35e10195dab3c99f/gtk-sharp.dll

Unhandled Exception: System.MissingMethodException: Method not found: 'System.Type.op_Inequality'.
  at MainWindow..ctor () [0x00000] in <filename unknown>:0
  at Couturier.MainClass.Main (System.String[] args) [0x00000] in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.MissingMethodException: Method not found: 'System.Type.op_Inequality'.
  at MainWindow..ctor () [0x00000] in <filename unknown>:0
  at Couturier.MainClass.Main (System.String[] args) [0x00000] in <filename unknown>:0

A workaround to fix it, is to start it with a specific runtime version:

  $ /usr/bin/mono --runtime=v4.0.30319 /usr/lib/couturier/Couturier.exe