Connecting to localhost problem

I am trying to connect to my localhost but am running into a problem. I am getting the error message of

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Adobe Dreamweaver CS3
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HTTP Error Code 404 File Not Found. Here are some possible reasons for the problem:

1) There is no testing server running on the server machine.
2) The testing server specified for this site does not map to the http://localhost/_mmServerScripts/MMHTTPDB.php URL. Verify that the URL Prefix maps to the root of the site.

I am duplicating the connection settings used for another site that connects without a problem. Local testing server is up and running, DB is open ...

Anyone be able to point me in the right direction?

gary