I have reinstalled this cleanly 4 times - including deleting application pool - and the result is always the same

Install goes without a itch them i press the view website button - the popup with he getting started page shows up, i close it and from then all popup Windows (module settings etc) show a 404 page.

Disabling popups allows module editing again (pages work outsider popup).
Also the jornal in the activity feed only shows to admins/superadmins

Any idea what could cause this?