SSO: "Internet Explorer cannot display the webpage"

Hi,

I configured SSO on our BO 4.0 SP7 platform. It works fine for almost all users, but there are some user which get a "Internet Explorer cannot display the webpage" message inside a small frame of at the LaunchPad Login page.

I found exactly the same case here http://www.forumtopics.com/busobj/viewtopic.php?t=170907&postdays=0&postorder=asc&start=0

The reason is probably a too high number of AD groups, the user is member of.

I have already set maxHttpHeaderSize="65536" at the server.xml.

We are not using a firewall.

.) Do you have any idea how to solve that?

.) Are there any other parameters which influence the maximum ticket size at tomcat?

.) Which logs are helpful to find out what's the reason?

Thanks!