312514 - Scrollthumb insistently jumps from bottom to top of vert. scrollbar in chatroom site

Status: RESOLVED DUPLICATE of bug 234291

(Firefox :: General, defect)

Description

[techno_plume-firefoxzilla]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a1) Gecko/20051014 Firefox/1.6a1
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a1) Gecko/20051014 Firefox/1.6a1

Using UK Yahoo! chatrooms via Firefox in Linux, scrollthumb insistently jumps to
the top of the scrollbar and perpetually requires pulling back down, to see the
newest chitchat in the window; making use of the site impractical. The 2
scrolling related options in advanced prefs don't affect bug. 

Presumably, the chat is Java based. Installed Sun JRE is working fine.
Issue occurs under Debian Etch Linux - in Windows XP (v.1.0.7) there are no
problems using the chatroom.

Reproducible: Always

Steps to Reproduce:
1. Access http://chat.yahoo.co.uk/
2. Login with Yahoo username+pwd and proceed into one of the rooms.
3. Await sufficient chat to initiate scrollbar, pull scrollthumb to bottom using
mouse.

Actual Results:  
Scrollthumb immediately jumps to top of scrollbar upon new line being added by
participating chatters. Dragging scrollthumb back down again merely causes it to
repeat its return to top. The outcome is that to promptly see the latest
addition to conversation you constantly need to drag the scrollthumb back down
again.

Expected Results:  
Functioned as on Windows XP Firefox v1.07 and earlier. There, scrollthumb
remains at bottom and text scrolls up within window from the bottom; ensuring
chat visible in 'real time'.

Not theme-specific, occurs with Default theme as well as Noia theme for example.
Present in regular Debian Etch (aka Testing) Firefox package [1.0.6-5]. Bug
duplicated in Firefox Trunk [via
http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/ - installed
on same date as bug submitted].