When trying to edit pages (with just some default blocks and with custom blocks as well) on a concrete5 - 5.6.3.1 install, I get an error overlay when saving the block with all the content on that page and when closing a block and opening it again it says "Acces denied". Now when refreshing the page, I'm logged out... so I can not edit ANY page at all. This didn't seem to be happening before on this particular site, and I was hoping someone else has had this problem as well, so I know how to fix this.

Any help would be greatly appreciated :)