I'm assuming you mean a previously existing thread that you clicked on, right?
Well, it's also been happening with some of the artwork threads, too. Rather then repeat myself, here's what I said in the Feedback section:
Source:
http://amaz0ns.com/option,com_smf/Itemid,135/topic,7010.8/It's my understanding (the Mighty L can correct me if I'm in error here), that like posting too much text (i.e. stories) causes the forum here to time-out, sometimes not only preventing subsequent replies, but even locking out the entire thread. At a guess, the same thing seems to be happening with frequently posted picture threads where too many ppl post pictures in a single posting, repeatedly.
The same is even more true with story postings, the answer, again, seems to be to break up your "installment" into smaller bites of several postings, otherwise a single large posting of a block of text will set off the lock-out glitch - which sometimes prevents subsequent reply postings, other times it locks out the entire thread altogether.
A while back I tried to post a story. Before I could even get a page down though the thread went entirely blank, I couldn't add anything or see what I had already posted. Has this problem been fixed yet or is it still happening? I really don't want to start posting a story only to find I can't finish posting it.