iPhone not connecting to iTunes since update Feb 2015

My iPhone 6 is not recognized by iTunes since the update which was released this week. The phone is recognized by my computer (Windows 8.1), but no joy with iTunes. I ran the update as I have been having problems for months now with iTunes buffering randomly when playing music. I called Apple, and they did not have an answer to the buffering problem, and I was hoping that the new update might work better. Note that the buffering problem does not occur if I use Microsoft music player or Spotify, so the problem is definitely with iTunes. I updated to the new update and iTunes is still buffering, and on top of that, I now can't connect my phone to it. What's going on? Apple, please sort this out!