bbPress.org

I am having an issue with the width of posts in a topic.

The first post displays correctly, but all consecutive posts are all too narrow.

You can see how it goes wrong via this link:

http://waterstadtoren.nl/forums/topic/test-topic/

Can someone tell me where and how I should fix this?

I did a clean “install” to no avail, this problem seems to stem from the original unedited files.