Hard to edit posts?

[Vax]

I don't know if it's just me but, in the Multi-Editor Project forum, when I try to edit my first posts, it's very hard to do so. First when I start typing to page goes all crazy and starts scrolling up, and when I try to copy and paste, it copy and pastes the whole thing. It happened for an old thread, then I made a new one, and I didn't have a problem until now. I don't know what it is, can somebody look into it?