I can edit every post I made, expect for the first posts on a topic (which you need to make when you start the topic) :(

It may be (probably is) multiple things. I don't post all too much, but that was the only consistent thing I have noticed causing the error (for me !).

I'm having this problem too, sometimes it takes two, three, or more edits for the edit to actually go through.

This definitely happened to me yesterday. I opened a new thread concerning a bug. Stupidly I pressed enter after creating the topic, so I had a blank board. I edited my post - adding the actual text - and today it is empty!

I can edit my posts but I notice half the time the site will eat the edit and act like you never did anything. Forces you to keep re-editing the post until it goes through.