The site is www.kindlebooks.co.za
I am not certain of my Drupal version but all my modules were up to date a few weeks ago. I am using Aquia Prosper as a theme and Uberdrupal as a profile.
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10 days ago my server was upgraded. I did not notice problems on this Drupal site at the time although I didn't test all functionality. The site has been quiet (which I assumed was due to the holidays), but it is receiving regular visitors based on Google Analytics.
A customer has written to say he could not get to the checkout, so I went into the site. The home page appeared, all was normal. I needed to log in as the administrator, it logged me in as usual. When I tried to enter one of the admin areas the result was a blank page. I tried to go back to the home page, and it is blank. After that almost every page was blank. (I use Firefox). I was able to get to the update page however, and I attempted to switch the site to maintenance mode. The result was a blank page - I have no idea if it worked or not.
I tried to rebuild the nodes, but the result was a blank page.
I opened the site in Chrome, and the home page appeared. I tried to log in, the result was a blank page. After that all pages have errors, but not a blank page - the message is