Hi Ray, thanks for responding,
The message I'm getting is:
"Unable to find file WA_Memento.htm in the Configuration/Floaters directory. The floaters will not be shown."
This was the same for CS3 and CS4, both with all the extensions successfully removed. I have since uninstalled and reinstalled DW CS3, as I want a clean install on which to add the extensions one-by-one to try to track down the problems I'm having with the other extensions. I'm not too keen on the idea of reinstalling CS4 too though.
I'll have a look for any reference to memento, and post back. Granted it's not a huge problem in the scale of things, but it's niggling away at me.