Wifi network listing freezes on Nexus 4 after Lollipop update
I had this problem recently and solved it by removing old saved networks in the WiFi settings. I found that there were a huge number of networks with names that were strings of letters and numbers.

To remove saved networks open 'Settings' and choose 'Wi-Fi' (and
wait for it to load).

From the 3-dot menu choose 'Saved networks'.

You should see a list of networks in a similar format to those shown below:


Remove any you don't recognise (tap the network name and tap 'Forget'):



Once all of the unrecognised names have been removed the list of WiFi networks should load without freezing the system.
NOTE: I have found that this can occur again after a while, in which case repeat the steps above.