are you adding CMS to a php page? make sure you have a php page open when trying add Power CMS.
At what point does it crash? when loading add the power CMS Content window? or after you have configured the settings?
have you tried these:
reset the workspace layout:
go to Window -> Work Space layout -> Reset '<your layout name>'
and Delete the Dreamweaver Cache file from the users configuration folder:
http://www.webassist.com/tutorials/Common-installation-issues