How to fix 'New mailing' that only has 'Initializing' and edit boxes that wait forever
This problem turns out to be a mis-configuration on the shared server. We were also getting Internal Error 500 messages just on signing in today, but the hosting company (vidahost.com) fixed the problem &amp; Civi is working fine now.  So not a problem with Civi, but a problem on the shared server, now fixed.  No wonder I couldn't find anything wrong with Civi..