can't install module diff

I've tried installing diff, but it doesn't appear anywhere in the list of modules. Can't work out why. I've installed one other module before which works ok.

It is in /sites/all/modules
I have the right version. It is diff-6.x-2.0.tar.gz & I am running D6.

I did try to translate it before install see this post http://drupal.org/node/323928
Then I removed the file I had created and ran update.php

I have found these entries in the log, don't know what they mean, but I think they have to do with update.php & not diff

locale 10/21/2008 - 15:24 Parsed JavaScript file misc/tableheader.js. vayira
locale 10/21/2008 - 15:24 Parsed JavaScript file misc/collapse.js. vayira
locale 10/21/2008 - 15:24 Parsed JavaScript file misc/drupal.js. vayira
locale 10/21/2008 - 15:24 Parsed JavaScript file misc/jquery.js. vayira

any suggestions?