When trying to use find and replace dreamweaver always crashes. I've tried clearing the cache from instructions of this link and it didn't work. http://forums.adobe.com/thread/494811
Does the issue occured after you made any H/w or S/w changes on your MAC(may be after upgrading your OS)?
If so, have you tried restoring dreamweaver's preferences? Follow the link below.
Make sure you backup all your current preferences if you need them again.