I have this same problem. Any time I click "Submit Reply", the button changes to "Saving" and doesn't go any further. I get the same issue with PM's. The only way I can check to see if the reply or pm was successful is to browse away from the page & go back.
Another "issue" is that I will refresh the forums and have a topic turn bold, showing that there was a new post or thread since the last time I went there. I'll click on the bold topic and no threads will show that they have new, unread posts. Sometimes the lag between the topic showing a new thread/post and the thread showing that there's unread posts can take 10 - 15 minutes. This issue is random unlike the posting issue.