If I post something too long, not really, just two pages long that I typed up, the post editor text block starts twitching, like in wordpress. It's very annoying. You type something in and it scrolls back to the beginning so you don't know what you just typed. Manually scrolling back to the bottom didn't work either. It keeps showing the beginning of the post while I'm typing the "second page". I don't know how to better describe it other than wordpress twitching editor!
I was having the same problem. I am using MS IE8 browser. I then clicked on the compatibility button next to the top address window in IE and the problem went away.
Lefty
Thank you Lefty. It worked. I just have to remember to write short posts and use a notepad and copy paste. 
Thanks Lefty. Helped me, too.
Hmm - I found this thread after seeing this myself today; switching to "compatibility" mode does fix it, but that's kinda a hack. Either the forum should be placed in "permanent" compatibility mode (using the meta-tag), or this issue needs to be fixed properly. Thanks to Lefty, all the same, though...
I am also experiencing the same behavior in IE8.