Previous Version was installed ok. Have CS6 on Win 7 x64. All fully up to date. After installing update to 3.5.2 via Your Updater, closed Extension Manager and reopened DW. Finish install procedure pops up but get error Message when click NEXT on opening screen of install procedure (click "canel" and you get same Message): "While executing onLoad in dmxAdvHTMLEdit30_install.htm, the following JavaScript error(s) occurred: In file "dmxAdvHTMLEdit30_install": initUI is not defined. Clicking OK just brings same Message up again. Only way to get out of the boxes in click red-cross top right in each window. After that removed Editor from Extension Manager and reinstalled from Updater. Same problem occurs after uninstall and reinstall.

Hi Ian,

Please clear your DW cache www.dmxzone.com/go/16740/clearing-dreamweaver-s-cache/

Yes that worked, but it does seem a bit strange to have to do this to install properly. Not only that, but after deleting the cache a New Error Message started to pop up many times. I had to close it again and again to get to where I wanted. The New Error Message said: "The following translators were not loaded due to errors: The following JavaScript error(s) occurred: Unable to open the script file "C:|Program Files (x86)|Adobe|Adobe Dreamweaver CS6|Configuration|Shared|DMXzone|CSS Navigation Menu|jQueryLib|jQueryComponent_lib-js (error 3)". It is a very long time ago since I removed CSS Navigation as I was not using it any more. To fix this New Error Message I have now reinstalled CSS Naviagtion. This also seems strange that I cannot do a clean uninstall of CSS Naviagtion. How can I do that?

Actually both of the errors are caused by a corrupted DW cache or configuration and if your DW installation is not corrupted, you do not have to this to install any of the extensions.
This is also explained in Adobe FAQs Section: forums.adobe.com/thread/494811

Thank you for the information and in particular for your prompt replies.