Yes, you are right! I have not recognized what is happening, the classifieds is not keeping the log in information from the forums. A user is needing to log in to the classifieds even though they're logged in the forums. I suppose this makes it an integration issue, or a cookie problem?
Forum settings show:User Registration System vb3
I seem to have some blocks showing that must be related to old installs. They may or may not matter.
In forum settings, there is:
UBBThreads Users: Default theme setting
Threads Users: We need to know what the site default theme setting is.
In cookie settings, there is:
Your Forum Cookie Name
Only needed for users of SMF, UBBThreads, WowBB and phpBB3 forums