If you have a WordPress installation and have been experiencing issues with Auto-upgrades, Plugin installation/upgrading, taking backups, it could be a problem with your server. A lot of 1and1 users will be familiar with this.
The issues are caused with the server having both PHP 4.0 and 5.0 installed. The workaround for this is very simple and straightforward. You need to instruct the server to use PHP 5 for parsing all PHP requests. This is done by appending the following lines to the.htaccess file in the root of your site:
Options All -Indexes
AddType x-mapp-php5 .php
AddHandler x-mapp-php5 .php
If there is no .htaccess file in the root folder (ususally www or htdocs or public_html) of your site (as in some cases), create a new text file on your desktop, rename it to .htaccess(remember to remove the .txt file extension), add the above lines, and upload to your server.
If there are any previous entries in the .htaccess file, append the above lines at the end of the file. But, make sure you do not remove/edit any of the lines that are already present.
Though this issue is noticed by most users on 1and1, any server which has two versions of PHP running is prone to these issues, and not just for WordPress but for any PHP application.