posts page doesn't work after permalinks changed

My site has a static homepage and a sepparate postpage with an index for all the posts. It all worked until I changed the permalinks into prettylinks. I installed htaccess and all the pages turned into pretty urls, except for the newspage that showed “Sorry, but you are looking for something that isn’t here.”

If I change it back again to default, then everything is fine again.

The posts itself are still visible and working through the sidebar

What can I do? (oh, and i’m not very technical)

Thanks!