Solved the problem 
Copied the content of the post, and reposted it, this time clicking the "submit your comment" straight away, and it worked. It was either some random glitch, or the "save and preview" is broken.
Just tested the "save and preview" with this post, and it worked fine. So it was probably just some random weird glitch.
This also happened to me many times - many minutes of labor got lost. This happened especially more when I had a free account - I had to upgrade to stop becoming frustrated. My idea is this (pending clarification by more knowledgeable persons):
If we spend too much time in making the posting, there is some sort of timeout - either due to the flash ads - flash ads are switched at regular intervals - or somebody already posted something in the meantime, making the page we are working on no longer current.
I found the following workaround work (most of the time, that is): before pressing submit button, select everything in the "Post you reply" or "Add your comments" space, then in the browser window select "Edit" => "Copy" - OR press Ctrl-C. Then press submit - if contents are lost, we can always "paste" the content back by "Edit" => "paste" OR Ctrl-V.
Hi, tried to post a new thread on the game analysis forum - wrote it, included a game with my analysis, and first clicked "save & preview" - I got referred to the "submit a new topic" page with an empty text box in front of me.
I clicked the "back" button on my browser, and fortunately the text hadn't been lost - so I clicked "Submit a new forum topic" and again I was taken to an empty "Submit new forum topic" page.
Clicked "back" again, and now both the "save & preview" and "submit new forum topic" are grayed out, and I can't click them. On another window I checked the forum - my message has not, at least yet, appeared there. I'm assuming that I'll have to redo my game analysis, as the post seems to be a lost cause.
Partly I'm testing with this message to see whether this was just some random glitch, or whether there's really some problem with the site, or my browser settings that's causing this. If this message gets through, can someone please advice me on what happened?