I have had real problem with BT broadband over the past couple of weeks for a range of websites. Did some diagnostics, turned out to be related to their default DNS servers. I have reconfigured my non-BT router to point to the free OpenDNS servers, and everything is much better.
Except NSC (using Chrome)... which sits with 'Processing request...' in bottom left corner, and the spinning 'loading' icon on the NSC tab.
For me, it seems to be the thread icons (e.g. cricket ball) and smileys that are causing the page to not load completely.