Visual Studio's "Start Without Debugging" option grayed out and F5 doesn't work

Ran into a very strange situation today. Suddenly, Visual Studio 2015 RC's debug options broke and the F5 key would no longer start the project in debug mode. Even IISExpress had disappeared, only showing "Start", which generated this error when clicked: "The debugger cannot continue running the process. Unable to start debugging."

Another issue: The References folder was empty, even though .NET 4.5.1 and 5.0 were added earlier.

I tried a repair via the uninstall utility but issue was still there. Finally, I exported and reset all the settings in Visual Studio following this article. Lo and behold: the options were back and I could run the app in debug or Ctrl-F5 (non-debug mode). Why this happened all of a sudden today, I don't know. I wasn't changing any settings, just editing a C# file when Visual Studio suddenly stopped working.

Whew!

Memory issues with IISExpress process on Visual Studio 2015

Visual Studio 2015 comes with IIS Express, which enables the localhost to serve as a web server without having to set up the app in Windows IIS. I was building a C#/MVC/Bootstrap site that kept crashing IIS Express. Some research revealed that we can run the server in 64-bit mode: Just go to Tools > Options > Projects and Solutions > check the box for "Use the 64 bit version of IIS Express for web sites and projects."

Memory usage by IIS Express went from over 700MB to 8MB now. Much better.