Testing from IE - post reply, then preview, then submit.
Still get the same 404 error.
(Able to post this with just 'post reply', then submit)
Should mention - the 404 error looks like a forum message error, it's not the browser 'generic' 404 error. The page still has all the other elements of the Cheat Happens message board, etc.
Testing to see if 'post reply' at the top of the message board (as opposed to 'post reply' on a specific message, like the first one I posted) makes any difference.
-edit - does not seem to make a difference. I get the same 404 when doing preview/submit regardless of which 'post reply' button I use.
I have had the same error occur from time to time. The only constant that I have noticed when I have this error is that it takes me awhile to compile the post (because of its brevity or simply because I had to leave the computer for a moment). In my case I have been able to hit the back button and return to the page where I originally typed my post and the message remains. From there I have then been able to skip the preview option and select submit. Hopefully those steps help you from losing your messages when you get this error. Unfortunately, I cannot specifically identify why it occurs (because it does not always happen). However, there are steps you can take to avoid having to re-type your entire post. Good luck.
--------------------------------------------------------------------------- -Mistakes- Perhaps your sole purpose in life is to serve as an example to others.