XDebug Client (which I assume you're using) uses Python's webbrowser module to launch your browser. Apparently, something is wrong with your Windows setup, or the way the default browser is defined has changed, as webbrowser's default functionality isn't working. You can try it by opening Sublime's console (View -> Show Console or Ctrl`) and entering the following code:
import webbrowser; webbrowser.open("https://www.google.com")
I would imagine based on your problem that IE will open.
The only way I know of to get around this, short of modifying the code for XDebug, is to set the BROWSER environment variable to the complete path to the Chrome executable. Once you do that, completely restart Sublime, reconnect to your PHP server, and see if Chrome now works. You can also try the above code again.
Good luck!