Mozilla has released Firefox 3.6.9, updating the popular Web browser with support for the X-FRAME-OPTIONS HTTP response header that enables Web site owners to prevent their content from being embedded in other sites, which can lead to clickjacking attacks. The update also addresses a number of security vulnerabilities and bugs, some of which could result in crashes. (Free, 19 MB)
I get a double dropdown window with a Java error message whenever I open this version.
That's really odd - perhaps check that all your extensions and add-ons are up-to-date (and disable or uninstall any you're not using)? You could also move your profile (in ~/Library/Application Support/Firefox) out of the of the way and see if that changed anything (put it back if it doesn't).