I noticed that if you edit the post heading after you publish a post, it is not updated in "last post" section under http://www.coderanch.com/forums. For example "Happy Brithday" was corrected to "Happy Birthday", but the change did not reflect on the main page ->
http://www.coderanch.com/forums. Not sure if it is a one off.
Yes, there's caching going on, and not all caches are always updated or invalidated when they should be. This particular case is actually fairly easy to fix, so we'll do that for the next release of the forum software.