I have had this happen both yesterday and today:

A thread is listed with a new response(s) on the "posts since last visit" page. When I enter the thread, the new response(s) are not there.

For example, in the "ADEA and retiree LTD plan" thread right now, I can only see the original question, even though a reply is there.

Yesterday, it happened on my thread about JCWAA rates and Section 404. I was able to "force" seeing the replies by hitting the "reply" button, which then brought up all of the replies under the entry box. Then I just left without replying.

This is a "caching" problem; your browser is showing you a version of the page that you viewed previously, rather than the current version of the page (that includes the missing reply).

I have changed a setting on the web server so that pages aren't cached (actually, they're set to expire 1 second after you view the page) ... this problem should go away now, though you might have to do the refresh/reload dance for pages that you've viewed up until today (April 2, 11:19 a.m. Eastern time).

Please let me know if the attempted fix is successful. (Post a reply message into this topic.) Thanks!