After upgrading to WP 3.8 at the weekend, my Mulitsites have been running VERY slowly and I've been getting errors stating "Your server may not be able to connect to sites running on it. Error message: couldn't connect to host".
I eventually removed the multisite settings (and all sub-sites) and access was to restored to normal.
I've seen in another post, the comment "All i had to do to fix this was to add a line to /etc/hosts, containing a list of the hosted domains: 127.0.1.1 domain1.com domain2.com domain3.com example.net" and this seems to give the reason why.
BUT - IS this the cause of the problem and, if so, is there a fix that can be installed without having to completely remove the Multisite facilities and sites ? ( Hope this makes sense! )