Styles button disabled in Announcement List

Hi,

We have an Announcements list on our Sharepoint 2010 SP1 and are having some problems with styles editing.

In fact, the button is disabled and we cannot format the text as we want. We have added some styles for our users to be able to quickly format text.

I've searched the web but didn't find anything. When I mouse over the button it says something is not activated or I don't have the correct permission (btw, I'm a farm admin member !).

Thanks for your help,

regards,

-- Julien Network & System Admin. // BPOS admin.