The disappearing-read-marks bug hasn't been conclusively traced back to the wwwthreads software. It could be in the database code. I looked for it in the wwwthreads support forums and couldn't find it, meaning that it looks like no other wwwthreads users have had it happen.

You need to look harder.

Subject: 5.1.5 "new post" bug
Subject: postlists marks new > no new.

Note that in both cases the bug was happening on their own forums, and they still haven't been able to figure it out.

Borislav