I'm not sure what's going on here, but I've been getting the same error every few weeks for several months now. It usually starts off with a 403 error and when I call my web host, they say that the index.php file is missing. I'm not sure how that could happen since I'm the only one with the password to my ftp.
No biggie. Just re-upload the index.php file from a backup. Only problem is, I get this:
Warning: require(./wp-blog-header.php) [function.require]: failed to open stream: No such file or directory in /homepages/46/d255400443/htdocs/albotasblog/index.php on line 17
Fatal error: require() [function.require]: Failed opening required './wp-blog-header.php' (include_path='.:/usr/lib/php5') in /homepages/46/d255400443/htdocs/albotasblog/index.php on line 17
Looks like the wp-blog-header.php file is missing. When I replace it, I get another error stating that another file is missing and when I upload the file I get another error and so on.
It seems like this happens at least once or twice a month and I'd just like to know what could be causing it and how to prevent it.