Hi again,
after a lot of debugging i think i found the solution.
The application is not loosing the session itself.
Something in the code of cuteeditor causes the webroot to be called in the background (maybe some base-tag?)
On the defined default page (index.aspx) we made a logout in our database based on the .net-session.
So there was no logged-in-status for the user anymore.
On my localhost i haven't defined a default page so the index.aspx wasn't called.
It doesn't seem to happen in Firefox.
Hope that helps,
mda