You can disable preview from the menu Edit->WebAssist Preferences...
Let me know if that fixes the problem. I will log a bug that we should add an auto recovery system to prevent loss of work in a crash as well.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.