The error "InitializeUI is not defined" Is associated with a problem with the Dreamweaver Cache file. I have yet to find a case of this error where deleting the cache file did not resolve it. I some extreme cases, I have found that you need to Restart the computer, then delete the cache file.
Please try restarting and deleting the cache file once again.
Also, Do you have multiple versions of Dreamweaver installed? If so delete the cache file for all of them.