Exception: Mutex could not be created

Today I was stuck for the first time with this:
System.InvalidOperationException: Mutex could not be created.

Context:
In a VPC I installed and launched VS2005, installed IIS, then created a new ASP.NET 2.0 website.

Short solution by Google:
Restart the server

Long explanation by Jerry Orman:
http://blogs.msdn.com/jorman/archive/2006/07/24/system-invalidoperationexception-mutex-could-not-be-created.aspx