When i click on Preview, I am faced with an empty forum text box.
Last I checked, I have the same problem. However, the preview button for replies to posts works correctly.
I don't know what causes the problem, but a possible workaround is to copy-paste your post into a reply to any open topic and use the preview button there. Also, these forums are relatively slowly-moving, which means that you usually have plenty of opportunities to edit your post for typos, fix formatting, etc. after you post it.