I've had my problem users try it again with the cookies improvement but without uccess.
Here are the symptoms again.
This happens to maybe a few dozen of my 2000 users. They can login to the forums no problem. The classifieds login says they are successful but then classifieds boots them back to the main screen not logged in.
The cookies issue above helped existing users in that once logged in to either classifieds or forums, they don't need to login again if they switch to the other application.
I've had the problem users reboot and erase their cookies to no avail.