Problem with forums in Linux

I am running Ubuntu Linux 8.04 Hardy Heron.

With the Firefox Web browser version 3.0.1

When I try to post on the forums no cursor appears, and I can not move the invisible cursor, in other words after I type something I cant delete it without holding the backspace key down and deleting eveything after it. The arrow keys do not work as well. This is more a pain while trying to edit your post. I was wondering if anyone else has this problem as I have no other errors on the forum, just this.