I am having the same issue...
I am using Win 7 and DW CS4...
I installed the CSS Design Suite a few days ago....Realized it wasn't for us, right now.
Immediately after successful install via AEM I get 4 dialog boxes on start up which read,
"Unable to find file WA_Sitetools_htm in the Configurations/Floaters directory. The floater will not be shown."
The other three dialog boxes say the same thing other than replacing the word "Sitetools" with "Progress_htm, wa_themeit.htm and WA_Memento.htm"
The first thing I did once realizing this is happening is delete the Wincache****.dat file<not sure of spelling but I followed the instructions at this site. To no avail the issue still exists.
I did notice while browsing around in the back that there are still remnants of these extensions. temp folder holds a site created with WA but that site has since been deleted and there is a WA_TIR folder which I do not know what is for...
Any help with this would be greatly appreciated as we need DW to run as efficiently as possible.