Monodevelop crashes on startup

(The following is copied from my forum post)

So, when i try to open ANY script in ANY project, my monodevelop sends it's build in error message, not saying anything, but telling me that some error happened, and asking me if i wish to send the report to developers or something, so they improve monodevelop-unity... After i choose something from there, the monodevelop continues loading what it started, and then crashes.... Looks like this: A fatal error has occured Blablabla, details can be send to Xmarian, do you want to do it... And then show more says:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.TypeInitializationException: The type initializer for 'Boo.Lang.Compiler.CompilerParameters' threw an exception. ---> System.TypeInitializationException: The type initializer for 'Boo.Lang.Compiler.TypeSystem.Types' threw an exception. ---> System.TypeLoadException: Could not load type 'System.Runtime.CompilerServices.ExtensionAttribute' from assembly 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. at Boo.Lang.Compiler.TypeSystem.Types..cctor() --- End of inner exception stack trace --- at Boo.Lang.Compiler.TypeSystem.Reflection.ReflectionTypeSystemProvider.ObjectTypeImpl..ctor(IReflectionTypeSystemProvider provider) at Boo.Lang.Compiler.TypeSystem.Reflection.ReflectionTypeSystemProvider..ctor() at UnityScript.UnityScriptCompilerParameters..ctor(Boolean loadDefaultReferences) at UnityScript.UnityScriptCompilerParameters..ctor() at UnityScript.UnityScriptCompiler..ctor() at UnityScript.MonoDevelop.ProjectModel.UnityScriptParserModule.ParseUnityScript(String fileName, String content) at UnityScript.MonoDevelop.ProjectModel.UnityScriptParser.Parse(Boolean storeAst, String fileName, TextReader reader, Project project) at MonoDevelop.Ide.TypeSystem.TypeSystemParser.Parse(Boolean storeAst, String fileName, Project project) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemParser.cs:line 72 at MonoDevelop.Ide.TypeSystem.TypeSystemService.ParsingJob.Run(IProgressMonitor monitor) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemService.cs:line 2108 at MonoDevelop.Ide.TypeSystem.TypeSystemService.ConsumeParsingQueue() in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemService.cs:line 2374 --- End of inner exception stack trace --- at Boo.Lang.Compiler.CompilerParameters..ctor() at Boo.Lang.Compiler.BooCompiler..ctor() at Boo.MonoDevelop.ProjectModel.BooParser..ctor() --- End of inner exception stack trace --- at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) at System.Activator.CreateInstance(Type type, Boolean nonPublic) at Mono.Addins.TypeExtensionNode.CreateInstance() in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\external\mono-addins\Mono.Addins\Mono.Addins\TypeExtensionNode.cs:line 93 at MonoDevelop.Ide.TypeSystem.TypeSystemParserNode.get_Parser() in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemParserNode.cs:line 63 at MonoDevelop.Ide.TypeSystem.TypeSystemService.GetParser(String mimeType, String buildAction) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemService.cs:line 282 at MonoDevelop.Ide.TypeSystem.TypeSystemService.ParseFile(Project project, String fileName, String mimeType, TextReader content) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemService.cs:line 336 at MonoDevelop.Ide.TypeSystem.TypeSystemService.ParseFile(Project project, String fileName, String mimeType, String content) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemService.cs:line 385 at MonoDevelop.Ide.TypeSystem.TypeSystemService.ParseFile(Project project, String fileName) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\TypeSystemService.cs:line 331 at MonoDevelop.Ide.TypeSystem.ProjectCommentTags.Update(Project project) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.TypeSystem\ProjectCommentTags.cs:line 73 at MonoDevelop.Ide.Tasks.CommentTasksView.<>c_DisplayClass2.b_1(Object param0) in c:\BuildAgent\work\d478831d940d36a4\monodevelop\main\src\core\MonoDevelop.Ide\MonoDevelop.Ide.Tasks\CommentTasksView.cs:line 206 at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() at System.Threading.ThreadPoolWorkQueue.Dispatch() at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()

What the hell happened here ? Please help people.