freelinking works only in preview

Problem/Motivation

I followed the wiki tutorial by david mccan here. When I finally create a wiki page with freelinking,
I see the correct link in preview. But after saving I find the raw text I entered.
Same behaviour if content exists or not. I also tried with freelinking being the only
input filter - it did not work out either.

The environment is:

• drupal 7.15
• LAMP stack
• Attachment provides a list of enabled modules

Thanks in advance!