iTunes slow movie download and does not resume after paused playback

iTunes 12.1.0.50 on OS X 10.8.5 MacBook Air is showing weird behavior recently. When I rent a movie from the iTunes store I have the following problems:

1. download is incredibly slow (ETA keeps going up to several hours) and


2. the movie will freeze when I unpause movie playback.

iTunes is basically unusable in this state. Did you ever come across a similar problem? Any ideas how to solve it?

What I tried so far (will update):

• Onyx system cleanup


• Re-download re-install iTunes