After upgrade to 2.7, website not loading anymore!

I’ve just upgraded from 2.5 to 2.7 via the upgrade link provided by my server (Linux). It told me the upgrade was successful.

But the website doesn’t load anymore! It stays blank for ages, trying to load, but with no success. The same happens when I try to login into the admin area.

The good news is I’ve checked my files on the server and I can see the SQL database is still here, with all my previous posts so the data isn’t lost, which is the only reassuring thing in this situation.

By the way, I decided to upgrade because my previous version was a bit buggy, a couple of things, including scheduling a post, didn’t work (I have another blog with 2.5 so I know that something was wrong with this one, as things that worked on the other didn’t work on this one).