I had a similar problem recently. Every single page of my blog turned up blank when I tried to access it, even wp-login and admin so I had no way of getting to the dashboard. I hadn’t touched to blog for about a week and I didn’t do any upgrades recently so this came totally by surprise. It took me an hour to find the cause which was wp-cache. I had to use ftp to deleted that plugin and the cache, everything went back to normal afterwards.
