SOLVED for me: I had the same issue. Firefox 3.6 was just fine loading pages, switching between tabs, etc. Firefox 8 & 9 were just awful - not just page load speed, but switching between loaded tabs, accessing Firefox menus - everything was really poky. I did an uninstall with RevoUninstaller, then made sure every trace of FF was gone, and then did a clean reinstall of FF 9.1 - still the same problem. FF 9 ran just fine in Safe mode, so I disabled all plugins, and no extensions were installed yet, but no difference. Then I looked over Help/Troubleshooting from the FF 9 menu, and noticed that OpenGL might be enabled for faster graphics rendering. I know that other apps (Photoshop) can actually slow down if your video card doesn't fully support OpenGL acceleration. TRY THIS: So I looked in FF Options/Advanced and noticed under the General tab that hardware acceleration is checked by default. I UNchecked hardware acceleration and now it's back to normal - and somewhat faster than 3.6. YAY! I'm not sure if my OpenGL theory is correct, but that fixed the slowness for me. (running Windows 7 64-bit with a first generation AMD 64 X2 Dual Core; Nvidia Geforce 6800 video card) Sam