It's not clear to me if this problem is site specific or if it's affecting everything. Can you create a new site definition and establish a connection to your database?
Try disabling Extensions.
Troubleshoot JavaScript errors | Dreamweaver CS4, CS5, CS5.5, CS6
If all else fails, use the CC Cleaner Tools below followed by a software re-install.
http://helpx.adobe.com/creative-suite/kb/cs5-cleaner-tool-installation-problems.html
Nancy O.