openTK doesn't build on Mac OSX 10.5.8 - GDIplus trouble?

I am a first time openTK user.
I can't install openTK with Mono 2.10.5 framework on my Mac OSX 10.5.8 => see log below

The problems seems to be the GDIplus library installation (Tool exited with code: 1. Output: Error: Invalid ResX input.
Position: Line 127, Column 5. Inner exception: An exception was thrown by the type initializer for System.Drawing.GDIplus)

Any ideas?
Thank you all!

/wolfgang

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http://www.opentk.com/ => pressed the "Download OpenTK" button
command used: xbuild OpenTK.sln /p:Configuration=Release
bash shell

iMac8,1 Intel Core 2 Duo 2.4 GHz
ATI Radeon HD 2400 XT
2GB Memory

% mono --version
Mono JIT compiler version 2.10.5 (tarball Mon Aug 22 20:38:08 EDT 2011)
Copyright (C) 2002-2011 Novell, Inc, Xamarin, Inc and Contributors. www.mono-project.com
TLS: normal
SIGSEGV: normal
Notification: kqueue
Architecture: x86
Disabled: none
Misc: debugger softdebug
LLVM: yes(2.9svn-mono)
GC: Included Boehm (with typed GC)

=======================================
Target CoreCompile:
Tool /Library/Frameworks/Mono.framework/Versions/2.10.5/bin/gmcs execution started with arguments: /noconfig /delaysign- /debug- /keyfile:../../OpenTK.snk /optimize+ /out:obj/Release/OpenTK.GLControl.dll ../GlobalAssemblyInfo.cs GLControlFactory.cs GLControl.Designer.cs DummyGLControl.cs GLControl.cs WinGLControl.cs IGLControl.cs X11GLControl.cs CarbonGLControl.cs Properties/AssemblyInfo.cs /target:library /unsafe+ /define:TRACE /doc:OpenTK.GLControl.xml /reference:/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/2.0/System.dll /reference:/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/2.0/System.Data.dll /reference:/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/2.0/System.Drawing.dll /reference:/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/2.0/System.Windows.Forms.dll /reference:/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/2.0/System.Xml.dll /reference:/Users/wolfgang/admin/opentk/Binaries/OpenTK/Release//OpenTK.dll /reference:/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/2.0/mscorlib.dll /warn:4
Target DeployOutputFiles:
Copying file from '/Users/wolfgang/admin/opentk/Source/GLControl/obj/Release/OpenTK.GLControl.dll' to '/Users/wolfgang/admin/opentk/Binaries/OpenTK/Release/OpenTK.GLControl.dll'
Done building project "/Users/wolfgang/admin/opentk/Source/GLControl/OpenTK.GLControl.csproj".
Project "/Users/wolfgang/admin/opentk/Source/Compatibility/OpenTK.Compatibility.csproj" (default target(s)):
Target PrepareForBuild:
Configuration: Release Platform: AnyCPU
Target GenerateResources:
Tool /Library/Frameworks/Mono.framework/Versions/2.10.5/bin/resgen2 execution started with arguments: /useSourcePath /compile "Properties/Resources.resx,obj/Release/OpenTK.Compatibility.Properties.Resources.resources"
/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/4.0/Microsoft.Common.targets: error : Tool exited with code: 1. Output: Error: Invalid ResX input.
Position: Line 123, Column 5.
Inner exception: An exception was thrown by the type initializer for System.Drawing.GDIPlus

Task "GenerateResource" execution -- FAILED
Done building target "GenerateResources" in project "/Users/wolfgang/admin/opentk/Source/Compatibility/OpenTK.Compatibility.csproj".-- FAILED
Done building project "/Users/wolfgang/admin/opentk/Source/Compatibility/OpenTK.Compatibility.csproj".-- FAILED
Project "/Users/wolfgang/admin/opentk/Source/Examples/OpenTK.Examples.csproj" (default target(s)):
Target PrepareForBuild:
Configuration: Release Platform: AnyCPU
Target GenerateResources:
Tool /Library/Frameworks/Mono.framework/Versions/2.10.5/bin/resgen2 execution started with arguments: /useSourcePath /compile "Properties/Resources.resx,obj/Release/OpenTK.Examples.Properties.Resources.resources"
/Library/Frameworks/Mono.framework/Versions/2.10.5/lib/mono/4.0/Microsoft.Common.targets: error : Tool exited with code: 1. Output: Error: Invalid ResX input.
Position: Line 127, Column 5.
Inner exception: An exception was thrown by the type initializer for System.Drawing.GDIPlus

Build FAILED.