here is what happens in dreamweaver cc 64bit windows 8.1
I make a form using dreamweaver forms, then I place my cursor where I want the captcha to go.
I then goto menu webassist|form|insert captcha.. click ok and it is inserted in the page ( I have learned because of the crash to do a cntrl s right away so my page is saved)
Now as long as my focus stays on the page, it seems to be fine BUT as soon as I move my mouse off page, say back to the menu, dreamweaver gives me the dreamweaver cc has stop and has me shut it down. If I come back in and open that page I can then move the mouse anywhere and it won't crash.
My thought is that the captcha plugin is not releasing from memory (flush) Once I shut down and go back dreamweaver is fine.