"... Cannot find or open the PDB file." ... Did I break something in my app?

[guardrex]

While running locally with IIS Express, an issue has come up (possibly due to something I fouled up), where I'm seeing many, many output lines like this:

'iisexpress.exe' (CoreCLR: dnx.coreclr.managed): Loaded 'C:\Users\abcde.dnx\runtimes\dnx-coreclr-win-x64.1.0.0-beta6\bin\System.Security.Cryptography.Hashing.Algorithms.dll'. Cannot find or open the PDB file.

The app is unresponsive as the runtime or IIS Express hits msdl.microsoft.com making requests for PDB files but reaches 404's, and yields ...

The program '[14616] iisexpress.exe' has exited with code -1 (0xffffffff).

... when I stop the debugger. Any idea what I might have broken? ... or is this an issue?

MVC.Core Web API app (dnxcore50 only) on dnx-coreclr-win-x64.1.0.0-beta6 in VS 2015 RTM

  "dependencies": {
    "Microsoft.AspNet.Mvc.Core": "6.0.0-beta6",
    "Microsoft.AspNet.Server.IIS": "1.0.0-beta6",
    "System.Runtime.Serialization.Primitives": "4.0.10-beta-*",
    "Microsoft.AspNet.Mvc.Formatters.Json": "6.0.0-beta6",
    "WindowsAzure.Storage": "5.0.1-preview",
    "Microsoft.Framework.Configuration": "1.0.0-beta6",
    "xunit.runner.aspnet": "2.0.0-aspnet-beta6-*"
  },

[guardrex]

Occurs in multiple applications. Paused the debugger and received this ...