The Just-In-Time debugger was launched without necessary security permission

I don't know if your problem had the same cause, but I got this error when trying to debug my app (just pressing F5).

We got crazy trying to figure why the w3wp.exe was failing with this error when minutes before it was running fine.

After some investigation we realized that the real problem was in the code of the global.asax: it was throwing an stack overflow exception (pretty ironic for answering here) and that was crashing the w3wp.exe process before VS could attach it to begin debug.

Fixing the buggy code made the VS to run nicely again.

I see the question is from long ago, but I hope it helps somebody.

To solve this issue, let the dialog help you. Agree to launch an elevated debugger and debug your problem. You probably have some sort of configuration problem. Your real problem isn't whether or not the debugger is elevated, it's the fact you need a debugger at all. In other words the first sentence on the dialog is "you have a problem." All the other sentences are "I would like to help you with that problem; is that cool with you?"