Comment 31 for bug 144216

This is an emerald bug. Removing emerald (and keeping compiz effects on) resolves this issue. Reinstalling emerald brings back the slow firefox behavior. When using emerald, the theme engine plays a role. Themes using the pixmap engine make firefox very responsive, almost as if there's no issue. The line engine is also decent. However, using the vrunner and other engines makes firefox tab switching slow. It's not just tab switching either.. for example, navigating items in Google Reader is slow depending on emerald/engine as well.

On Ubuntu 7.10 + all updates (also present when using the 8.04 Hardy kernel/nvidia drivers)

System:
HP Pavilion dv6700 Notebook
Intel(R) Core(TM)2 Duo CPU T9300 @ 2.50GHz
3GB RAM
NVIDIA GeForce 8400M GS (256MB)