recreate the users configuration folder as outlined in step 12 of the Adobe troubleshooting guide:
After recreating the configuration folder, open DW go to Commands -> Manage Extensions to open the extension manager, then close DW.
In the extension manager, uninstall each extension, then use the install button to browse to the extension MXP files and reinstall them.
After installing the extensions in the Extension manager, open DW to start the WebAssist Installer.
If the WebAssist installer does not open automatically, open a PHP page to launch it. When the WebAssist installer completes, make sure to restart DW.