All too often does one encounter a time when Safari will freeze and not respond to any input, and sometimes crashes altogether, losing any precious open webpages you didn't want to lose in the first place.
It's best to update to the latest Flash 10.1 because this latest version seems address some of the freezing in Safari, but unfortunately, not all of it.
If your browser becomes unresponsive due to Flash, you can use a very simple but effective Terminal technique:
Open Terminal using Spotlight (or however you wish to open it)
Type the following: killall -9 WebKitPluginHost
Now Terminal will quit all Flash Plugins in Safari, which will instantly stop the frozen state. You can then refresh the webpage to reload the plugin, hopefully without the freeze state occurring again anytime soon.