Problem Solved for me as well ...
I'm no longer getting the error messages but I did multiple tasks so I'm not sure if it helps anyone else but here's what I did.
Memento - Set to Never - Show on Dreamweaver Startup
RSS - Checked Disable all RSS Feeds and set Check for Updates to When Memento Opens. I also deleted the RSS Feed Subscriptions.
I downloaded the latest version of the FreeTools and installed but still got the errors so the above may have not mattered but thought I would mention it anyway.
I then deleted the WinCache file and chose to installed SecurityAssist over top of itself and did the same with ProMapsGoogle just for kicks. When prompted to replace newer existing files I chose Yes to all.
I rebooted my machine, started Dreamweaver (I have CS5) and got no errors. I tested all extensions and everything seems to be OK.
Hope this helps!