I'm definitely interested in the solution for this because I've got the same problem and it just started the other day. I can't use CSS Sculptor all of a sudden. I get the same javascript error. Except that I'm on a MAC OSX v10.6 with Dreamweaver CS4.
I've redownloaded the extension, removed it, and reinstalled it and it still doesn't work. I also get a cookies (I think it mentions something to do with cookies) javascript error pop up every once in awhile (when I open certain php pages). I don't remember the details, but next time it pops up, I'll get a screenshot. But that error doesn't prevent me from working. The one that this thread is describing DOES. Anyone have any ideas? Do I need to get a support ticket created? Since the solution probably won't be posted here.