Beware of current compatibility level set in your DB when configuring SQL Server Fulltext
In case it might help people having the same issues I found, I'm posting this here because it's related to the question.
I had a SQL Server DB installed by an external company. We asked for some modification to its software that required adding fulltext search features in the database.
I had a test database that I had created from scratch beside this company database to test the configuration of these services.
When I tried to create a Fulltext catalog in SQL Server 2008 all options where greyed out for the company's database, whereas in the database created from scratch everything was OK, the screen was not greyed out and I could for example state that I wanted accents to be ignored.
Out of despair, I started to compare every parameter between the two databases, and I found that that the company's database compatibility level was set to 'Sql Server 2000 (80)'. As soon as I changed that to 'SQL Server 2008 (100)', everything started to work fine, the Fulltext catalog creation scren was no longer greyed out.
I found a note, in this article somehow related to this compatibility issue:
https://msdn.microsoft.com/en-us/library/ms142583.aspx#OV_ft_predicates