Drupal 6.x production site - going live problems

I am hoping someone may be able to help point me in the right direction. I have been browsing the Drupal site and may have missed the information. Or maybe I should be posting this somewhere else.

This is all new to me and it may be something simple that has been missed, but here goes.

We have developed a community website using Drupal 6.x and a number of modules. I won't list them all now.

The main problem right now is an issue about people logging in and out. There are some quirks.

The modules we are using include the Front page module that seems essential for redirecting users by role to a page after they login.

We also wanted to use LoginToboggan but have disabled that module in case it is the cause of the problem which I will describe in a moment.

We would also like to use the Countdown Timer and Autologout modules but they have both also been disabled while we resolve this.

The problem:

If a user logins in and goes to some other pages on the site and then logs out. It appears as if the logout has been successful because they see the default front page, but the logged out message is not displayed.

However, if they can still use the back button in their browser they can still see the previous pages they were viewing when they were logged, probably from their cache.

If they then try to view a new page as if they were logged in, they can sometimes see it, e.g. their own blog page and other modules that an authenticated user can access but trying to use modules requiring admin status cannot be accessed even if the person original logged in as admin and then out.

Even disabling the Front page module does not fix this problem.

I don't know but it seems that Drupal 6.1 needs to remove a session cookie or something with log out. Or maybe we need to configure something on the server side.

This is a serious problem with taking the site live. Any help would be greatly appreciated.

Thanks in advance and please let me know if I should be placing this post elsewhere.

Izzy