Cause: You may be on a web host which runs PHP in apache mode without suexec but doesn't provide the FTP extension.

Solution: This is a fundamentally broken PHP setup, so you should consider finding a better web host. If that isn't possible, you'll have to download the .zip file from the customer downloads area and use the manual upgrade instructions in readme.html.

Cause: You may be on a web host which runs PHP in apache mode without suexec, but the FTP information you've provided at Admin -> Settings -> System is incorrect.

Solution: Make sure you've clicked the help icon next to the FTP area and understand how you're supposed to type the directory. Test and correct your FTP info.