I am trying to update wordpress from 3.6 to 3.7 using the updater in the admin backend. This is something that has always worked fine in the past on the server my site is on but for some reason when I click the "Update Now" button (which should run the script in
wp-admin/update-core.php the page hangs for a minute or two before going to a blank admin page (i.e. the wp-admin menu bars and header bar are there but there is no content in the body of the page).
Any idea what's causing this? I've tried deactivating some plugins but woocommerce must be kept on for as long as possible in case of an order going through - in any case I doubt it would cause this failure.
Edit: as a site note, my site runs on a VPS running Ubuntu 12.10 on Nginx with php 5.4.6. I also have a few other wordpress sites on the same server on different vhost. They are much simpler and use completely different themes and only a couple of simple plugins. The update still fails on them in the same way suggesting a server issue rather than an issue with themes or plugins.
As mentioned I will check logs but at work currently where ftp and ssh ports are blocked which makes it tricky.
Edit 2: Having reviewed the log an entry is recorded when I run the upload and it fails:
2013/10/29 23:20:48 [error] 9384#0: *5318248 upstream timed out (110: Connection timed out) while reading upstream, client: 188.8.131.52, server: www.sergedenimes.com, request: "POST /wp-admin/update-core.php?action=do-core-upgrade HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "sergedenimes.com", referrer: "http://sergedenimes.com/wp-admin/update-core.php"
I have tried restarting both php-fpm and Nginx to no avail. It looks like it could be a server config problem but the rest of the site works flawlessly (including updating plugins). The issue is not specific to just this site. On my VPS I have 3 other WordPress sites running on separate vhosts that all share the same update problem.
Any idea what the cause could be and how to solve?