I’ve just hit this again so I decided to share the solution in case anyone else hits this.
Symptom: Visual Studio freezes for about a minute after you hit F5 (but before the app actually starts), then suddenly unfreezes and happily proceeds to launch the app.
Cause: VS calls the Windows CreateFile function on one of the paths specified in Tools –> Options –> Debugging –> Symbols –> Symbol file (.pdb) locations and that location either doesn’t exist or can’t be accessed (e.g. due to misconfigured DNS settings).
Solution: Check that all network paths in the list above can be accessed normally.
If you launch ProcMon.exe before starting debugging and configure the filter to only monitor “devenv.exe”, Result = “BAD NETWORK PATH”, it should show you which CreateFile call causes a network timeout.