After installing version 5.0 of the Safari browser, a few people are reporting the program crashes whenever they try to open it. Even after trying some general troubleshooting steps the browser still crashes, which could mean something small has been overlooked, but also could mean there was a problem with the installation.
To start the troubleshooting, first determine if the problem is account-specific by either going to another existing account, but also by creating a fresh user account to try. Even if other existing accounts have similar problems, using a fresh one will ensure no modifications have been made.
If the problem only happens in one or a few accounts, then it is likely the problem is because of a faulty setting or plug-in that resides in the local account. As a first step, try removing Safari's preferences, which are located in the /username/Library/Utilities/ folder and are called "com.apple.Safari.plist." Remove that file from its folder and try relaunching Safari.
You might also try clearing your Web caches, which can be done with Safari using the "Reset Safari" feature if you manage to get it open; however, if not then you can use a cache cleaning program like OnyX or Snow Leopard Cache Cleaner to remove the browser caches.
If this does not clear the problem, next try launching Safari without plugins enabled. To do this, go to the Safari preference file mentioned above and open it with a text editor. Locate the "WebKitPluginsEnabled" key and change it from "true" to "false" so it looks like the following:
This should prevent Safari from loading plugins, so save the file and relaunch Safari to test it out. This setting can be set in the "Security" section of the Safari preferences; however, if the program will not launch then this is an alternative way to disable the plugins.
While disabling the plugins should keep Safari launching in a bare state, you can also try removing plugins manually. These are located in the following folders, so move all of them from these folders to another location and try relaunching the program.
If the program launches after doing this, then test each plugin (or small groups of plugins) by moving them back one by one and relaunching the browser each time.
Lastly, with plugins removed from the global library, try booting into Safe Mode and launching Safari from a fresh user account. If this still does not work, then download and reinstall Safari again, especially if you used Software Update to apply the previous update. A faulty installation can sometimes be remedied by reinstalling the program without using updaters (similar to reapplying a system "Combo" updater when OS updates cause bizarre problems. Before doing this you might consider runningprocedures on your system and install it when booted into Safe Mode to ensure minimal interference from other system processes.