Internal Compiler Error

I am getting an this error message Internal compiler error. See the console log for more information. output was: Unhandled Exception: System.TypeLoadException: Could not load type 'System.Func1' from assembly 'mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e'.

at (wrapper managed-to-native) System.Reflection.MonoMethodInfo:get_method_info (intptr,System.Reflection.MonoMethodInfo&)

at System.Reflection.MonoMethodInfo.GetMethodInfo (IntPtr handle) [0x00000] in :0

at System.Reflection.MonoMethodInfo.GetAttributes (IntPtr handle) [0x00000] in :0

at System.Reflection.MonoMethod.get_Attributes () [0x00000] in :0 `

After i had an issue with monodevelop which wouldn't let me to switch to any other windows (not even task manager) so i had to log out with CRTL-ALT-DEL and when i booted the project back up it ran but didn't work correctly. I then tried to build and run the project and it came up with the above message and i haven't been able to do anything since. It is also saying that none of my scripts (including the ones from unity itself) are compiled.