Permalink going wrong, duplicate subfolder in url

Dear All,

I am using a multisite setup for my website.
For the news page and other regularly updated pages I use a blog.

I originally started with the twenty eleven theme, which adds previous and next links to the bottom of the posts.
I have set up my news page to show the 5 most recent posts.
http://www.fortherestless.com/news/

so at the bottom the “previous” url (in this case called “the past”) button looks like this
http://www.fortherestless.com/news/page/2/

I however encounter a problem.
for the tour page I have set the number of most recent posts to 1.
Each post resembles one year, so when a new tour comes up I can just make a new post and it automatically shows the current year.

The previous links here do something odd, they add the subfolder twice in the url.
http://www.fortherestless.com/tour/tour/page/2/

so that’s one “Tour” to many in that link.

When I change the numer of blog posts to 2, everything seems to work fine and the url drops the extra “tour”.
So I’m guessing it has something to do with the basics of the theme,
but for the life of me I can’t figure out where, probably in single.php ?

Anybody know what to change or add ?

thank you in advance.