Installer Validation - No errors, but I don't get further

I am trying to install Modx 0.9.6.1 on my localhost. Apache2, php5, mysql, on Ubuntu Gutsy Gibbon.

Database configuration seems successful, I got no warnings here. I am getting as far as the pre-installation validator. I first just unzipped the files, filled in the config data into the page presented by Modx, and got six error messages. I acted conformingly and set the permissions as requested. That worked insofar as in all the lines, there was a nice green "OK" after that. But still, in the summary, I am told that because of these (0) errors, I am unable to continue the installation.

Then I deleted everything, unzipped anew and set the permissions straight away. But that didn’t help. Then I tried again with the 0.9.6 version of Modx, to no avail.

I have the system in German, and the relevant part of the error message is:
Leider kann die Installation nicht fortgesetzt werden wegen oben aufgeführter Gründe. Fehler.

I don’t know the English version, but it seems that where the number of errors would have been, there is nothing, in front of the word "Fehler", for "errors".

I would appreciate any help, as I am clueless by now.
Cheers,
René

This should be a bug in the german lang file. I switched the lang to english, and an error showed up, telling me that the cache dir was not writeable. Correct. I set it writeable and could go on. In the German installation process, it really did not show up!

Perhaps someone should check this.