I was able to post a reply to the thread using the 'quick reply' box at the end of the thread. But yes, if you click reply and try to post a reply the traditional way, there seems to be an issue with posting.
I'd suggest using the quick reply box for now which should let you comment to the thread, and I'll have HDS look at the thread for what is exactly wrong with it when he has some time.
Myriads