I've noticed several times that the "Last post" info in the posts listing page for a forum does not match the actual thread it refers to.
For example, this thread (Windows Me has only 16 colors
The last person to post on this thread was myself, on 12/20/2009
yet on the Windows 95/98/Me postings list for that thread ("Windows Me has only 16 colours") it says
"Last post 07/17/2010 by susanca"
There is nothing posted by "susanca" in that thread as far as I can see.