Monodevelopement not responding?

When I tried to edit a C# Script file, by double clicking on it, monodevelopment did not start up so I could edit? I need to for my game… so please help? Thanks in advance!

PS-
It says, “Unable to open Assets/Scripts/Health.cs: Check External Application Refrences”

Check external tools section of preferences. Make sure it is set to MonoDevelop.

Help? The other person didnt help at all…