vertical scrolling stops on some forum pages

[puppet]

Binary package hint: firefox-3.0

Description: Ubuntu 8.04.3 LTS
Release: 8.04

the bug i want to report is similar to this one
https://bugs.launchpad.net/ubuntu/+source/firefox-3.0/+bug/315709

but:
it happens ALWAYS and (at the moment) only with forums
when, on forums, you have several posts one after another, let's say the first one is very long, the page seems messed up till you scroll to the next post (please check the examples)
it affects both linux and windows versions of firefox
it happens if you use the scroll wheel of the mouse or the page up/page down or arrows keys

examples:
http://www.motoclub-tingavert.it/t429368s.html
http://www.motoclub-tingavert.it/t305791s.html

ProblemType: Bug
Architecture: amd64
Date: Wed Aug 26 13:34:22 2009
DistroRelease: Ubuntu 8.04
Package: firefox-3.0 3.0.13+nobinonly-0ubuntu0.8.04.1
PackageArchitecture: amd64
ProcEnviron:
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: firefox-3.0
Uname: Linux 2.6.24-24-generic x86_64