I am unable to use MonoDevelop to open a script from Unity 5

Running Windows 8. When I double-click to open a C# script the MonoDevelop splash screen pops for half a second and then closes immediately. I have tried running as an administrator, killing and MonoDevelop tasks in Task Manager (there are none), downloading a new glibsharpglue-2.ddl, repairing .NET Framework 4.5. I have also tried changing the External Editor from “MonoDevelop (Built In)” to “MonoDevelop” and re-“Syncing MonoDevelop project”

Any other suggestions?

Are you running an anti-spyware-program? The first time i double-clicked to open a C#-script the anti-spyware-program asked me if i want to allow unity 5 to start mono-development. Perhaps something like this is preventing MonoDevelop to start.