Depending on your hosting provider, you may or not end up with portions of your WordPress blog (main site, admin site, plugins, etc.) that are completely hosed. Yes, that is a technical term.

Like I said – it all depends on your hosting provider. My blogs use 1and1, and I experienced this issue with my admin pages (<blog url>/wp-admin/) only. After about 30 minutes of spinning wheels, I discovered that there was an issue where the new WordPress admin pages were using PHP5 and the server was not set up to use PHP5.

All I had to do was add the following lines to my .htaccess file, located in the root of my blog’s file system, and everything started working like a charm.

Options All -Indexes

AddType x-mapp-php5 .php

AddHandler x-mapp-php5 .php