Linking problem

I have installed version 3.5 and now I am unable to make new links. The old links still work!

Every time I try to make a link I do not get the list of pages to choose from and if I add it manualy I automatically go to “Messages”.

Can anyone tell me what is wrong?

I have already tried installing another theme, but I get the same problem. Is there a bug in version 3.5?

Thanks for helping!

It concerns this document http://www.hetbalkonkamertje.nl/arrangementen/

The bold items “Dineren en slapen – arrangement (3 dagen/2 nachten)” and “Workshop vilten – arrangement (2 nachten – 3 dagen)” still need to be linked.