Hi I'm getting the same thing happen today despite not installing any new extensions. Dreamweaver was working perfectly yesterday but now I can't use any of my extensions and I'm getting messages just like you.
You could try disabling Memento from the Edit/Webassist preferences
Under memento - choose - Show on Dreamweaver start up never
Also disable the RSS feeds.
I say this because I have just looked in my support history as I had this problem once before (but when installing one of the extensions like yourself) and it was one of the suggestions.
However, the problem was only resolved when one of the support team remotely took over my computer and I can't now remember what they did.