I have now had the same problem on two differant computers so I'd be suprised if it was me.
What's happening is once I try typing a reply/post and I get to the bottom of the box the box get really jerky and I can't see what I'm typing. I can scroll down and see what I have typed but once I start typing again the page jumps back up and jerks everytime I type a character.

P.S I'm using IE, yeah yeah I know, but I hate Fire Fox
Lurch