I recognise the code from my howto. :)

IE7 or less prefixes the whole url before the #id of the tab in the href. So you need to add code to clean out before the # to get the correct tab ID.

Failing that, you can use IE conditional comments to show simple headings rather than tabs for old versions of IE.

(Or you could use Magic Tabs
http://www.concrete5.org/marketplace/addons/magic-tabs/... )

There is more about this in the support/form pages for Magic Tabs.

It is indeed your code !
What I did actually was to link the ccm.app.css file to the page and it works... Not sure if that's normal and logical but it did the trick