A couple of days ago I upgraded to Wordpress v2.6. After the upgrade I opened the blog, and added a new post. Both of those actions worked properly.
After the upgrade I noticed a major decrease in comment and trackback spam. But today I discovered the real reason why comments AND page views were close to zero.
There's a bug in Wordpress 2.6 where the permalinks are not working correctly. If you're using permalinks with the date, name, etc. (e.g. /index.php/switched-to-mac/) you get a 'Not Found' error. A definite WTF moment.
When you change the permalinks setup in the wordpress admin pages to default the pages/posts are accessible again. It seems that the issue is known and will be fixed in Wordpress 2.6.1. Untill then, most of the Google search results which end up on my website will result in a 'Not Found' error.
I would go back to an earlier version if I could. After the upgrade (which I thought that worked correctly) I removed the 2.5 installment... Yet another lesson for the future.
UPDATE: the pageviews are returning to normal :)