I use two factor authentication with my Google Apps, and while Google Talk was working fine before the install of Windows 8.1 preview, it stopped after it was installed.
Going to accounts.google.com and generating a new passpharse didn't help, but I found this:
I uninstalled Google Talk, and Google Talk plugin for Chrome and re-installed Google Talk from here:
I also reinstalled the Google Chrome voice and video plugin by starting a video call with a contact.
All seems to be working fine now.