I have created a new security group. I've assigned the permissions 'AssetAdmin' and 'CMS Main' to this group. Then I have created a member account of this group.
After I logged in with this account I tried to add a new page.
After I clicked on the "Save & Publish" Button I got the following error message:
'You've been logged out of the server, so we're going to send you back to the log-in screen.'