Internal compiler error. See the console log for more information. output

was:
Unhandled Exception: System.InvalidCastException: Cannot cast from source type to destination type.

  at Mono.CSharp.PendingImplementation.BaseImplements (System.Type iface_type, System.Reflection.MethodInfo mi, System.Reflection.MethodInfo& base_method) [0x00000] in <filename unknown>:0

  at Mono.CSharp.PendingImplementation.VerifyPendingMethods (Mono.CSharp.Report Report) [0x00000] in <filename unknown>:0

  at Mono.CSharp.TypeContainer.EmitType () [0x00000] in <filename unknown>:0

  at Mono.CSharp.RootContext.EmitCode () [0x00000] in <filename unknown>:0

  at Mono.CSharp.Driver.Compile () [0x00000] in <filename unknown>:0

  at Mono.CSharp.Driver.Main (System.String[] args) [0x00000] in <filename unknown>:0