Since Safari 5 came out, a few people have complained of the application crashing. A couple of weeks ago we wrote an article outlining some of the steps to take if the application crashes at launch, but other times the program will seem to crash on a more sporadic basis.
In addition to WebKit-based plug-ins, you may have some that use SIMBL (SIMple Bundle Loader), which are loaded separately from standard Internet plug-ins. Some common SIMBL-based add-ons are the Conduit "Community Toolbar" that has been a problem for many people, as well as some Ad Blockers.
The problem could be an issue with the current version of SIMBL, or with the specific plug-in being run by SIMBL. Either way, your best bet to start out with would be to remove SIMBL and any associated plug-ins, at least until the problem is addressed by an update to either of these items.
To remove SIMBL you have two options: you can either uninstall SIMBL itself or remove the specific plug-ins it is loading.
SIMBL is a small scripting addition program called "SIMBL.osax" that is installed in the /Macintosh HD/Library/ScriptingAdditions/ folder. In addition, it uses a Launch Agent file that is located in /Macintosh HD/Library/LaunchAgents/ and is called "net.culater.SIMBL.Agent.plist."
Removing these files will effectively remove SIMBL. If you just remove the launch agent, the program will still be around, and if you remove the program only, the launch agent will continually try to launch it.
Remove SIMBL plug-ins
If you wish to keep SIMBL installed, you can locate and remove specific SIMBL plug-ins from the following directories:
/Macintosh HD/Library/Application Support/SIMBL/Plugins/