644082 - Site extreme slow with animated GIFs

Status: RESOLVED DUPLICATE of bug 615063

(Firefox :: General, defect)

Description

[hsg_murdock]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.151 Safari/534.16
Build Identifier: Firefox 4.0 (final)

I am using a Burning Board web forum where on the reply site are about 100 small (about 30x30 px)animated GIFs. While these GIFs are shown, Firefox 4 is extremely slow. If I scroll down the site and the GIFs are not shown any more, everything is normal. All other browsers (including Firefox 3.6 and Chrome) do not have this problem. More interesting, the problem only occurs on two out of three of my computers:
On my "Intel Core Duo with Intel GMA 950 and Ubuntu 10.10 x86" and on my "AMD Athlon X4 640 with ATI Radeon 4300 and Windows 7 x64", the problem occurs.
But on my "Intel Core i5 750 with Geforce GTX 260 and Windows 7 x64", everything is _fine_.


Reproducible: Always

Steps to Reproduce:
1. Go to the website
2. See it slowing down
3.
Actual Results:  
The whole browser becomes very slow and the CPU load rises.

Expected Results:  
FF4 should not slow down.

I also tried to reinstall FF4 with wiping all user data (complete clean install, no addons, etc.). Didn't help.