Firefox 1.0.6 stability update released, but this time they recommend uninstalling previous versions of Firefox first.
1. Read the Firefox 1.0.6 Release Notes
2. Download the Firefox 1.0.6
3. Close all windows.
4. Uninstall previous versions of Firefox 1.0.x. Uninstalling previous versions doesn’t erase your Firefox profile.
5. Run the Firefox 1.0.6 setup executable.
6. After the install, some older Firefox extensions may need updating. Check for updates at the Firefox