Firefox 3.6.4 is the last major release before the eventual Firefox 4.0, to be released in Nov 2010. Release candidate of Firefox 3.6.4 was available for download on the last week of May 2010, and it was expected that the final release of Firefox 3.6.4 would happen in the first week of June 2010. But Mozilla delayed the release for a few weeks to smoothen out the rough edges that came to haunt the release candidate of Firefox 3.6.4.
What's New in Firefox 3.6.4?
Mozilla had decided to push the final release of Firefox 3.6.4 for a few weeks owing to the issues that originated with the last release candidate of Firefox 3.6.4. Firefox 3.6.4 was originally meant to be named as Firefox 3.7. But later Mozilla decided to rename the version 3.7 with Firefox 3.6.4.
Firefox 3.6.4 is meant to be more stable than the previous releases of Firefox. A bulk of Firefox's instability was caused by third party plugins, which ironically, is what Firefox is so famous for. But Mozilla have find a way out of this problem with Firefox 3.6.4. Firefox 3.6.4 “will include the Crash Protection for ‘out of process plugins’ feature to help create a smoother, faster and more secure browsing experience for users”. This feature reportedly have worked wonders with Firefox's stability related concerns.
Initial builds of Firefox 3.6.4 started arriving in April 2010 and that was when Mozilla debuted its "Lorentz" project. According to Mozilla, Lorentz project helped a lot in stabilizing the browsing experience for Windows and Linux users who have installed Adobe Flash, Apple Quicktime, or Microsoft Silverlight plugins. "If a crash in one of these plugins happens, Firefox will continue to run and users will be able to submit a crash report before reloading the page to try again."