I recently responded to a thread about imaging of the apollo landing sites by a satellite currently in orbit 50 km above the moon, but which will be dipping down to 20 km. Some numbers/calculations that sort of thing.
When I am logged in, this post shows up as the most recent forum post (presumably, it won't anymore after I post this, but should still be in the 20 most recent). When I am not logged in, it doesn't, and a post by Count Zero (made before mine, in the same thread) shows up. Either way, if I click on the thread title, I don't see my post. This dodgy behaviour is happening under both Firefox and Safari, so it doesn't seem browser specific; I cleared all history (including cookies) in Firefox and it didn't fix the problem.