Log In Problem

Hi,
I have a problem with the VTE Log In.
When I try to Log Out with my username and Log In with another username, the page doesn't load.
The problem is:

"Safari cannot open the page. This might happen when you open a page that redirects to another page that redirects to the original page"

If I delete the cookies, the page works again.
How can I fix this problem??
Many thanks