Cannot use links on EHCP


I have troubles with EHCP. I can't more use links
on my EHCP Panel, for example domains, or All clients.
The links in Tools all ok. And in Main Menu not ok, if I klick oh this links, I get right now a login menu with username and password for EHCP Panel login. Than after login, I try to klick on domains again, but immediately come login for EHCP Panel. Do you know about this trouble?