Today I installed a Joomla site because I have a contract to do some development in Joomla.

So... I started, looks real nice and stuff, clicked next, next and got and error. It tells me that the configuration.php file is not writable and that I'll have to copy and paste once I'm finished or make it writable. Well... I thus copy configure.php-dist as configure.php and try again.

That makes it fail a little later with the following error:

  the XML response that was returned from the server is invalid

The fact is that whenever you run the last step or try to install the default data, there is an access to the site that attempts to configure itself with the configure.php file. Up to here, that makes sense... but the result is that the default Joomla configuration options kick in! And those are totally invalid for most people.

Deleting the file is the solution. And restart your install (i.e. use Previous back to the start and try again).

The idea of the configuration file is that if you know enough you can edit it yourself and go with it without having to run a website install.

To eliminate the error, I'd bet that what you'd really have to do is a chmod 777 on your root folder, where Joomla will create the configuration.php. Otherwise. an empty configuration.php file would probably do. I'd suggest the Joomla people to include such a file in their package so newbies like me don't have to fiddle around like this!