g1smd - 10:10 pm on Sep 28, 2006 (gmt 0)

Well, that is two different URLs leading to the exact same content, so that is classic "duplicate content".

Get your .htaccess file to rewrite one form to the other, and issue the "301" for the original one. That will cure it.

Which one, and which way, is up to you...

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Don't worry about any URLs that appear as Supplemental Results after they have been turned into redirects. That is normal. Google hangs on to URLs that return a 301 or a 404 for one year after they start doing so.

They do NOT count as Duplicate Content if their HTTP code is 301 or 404. They will get cleaned up soon enough.

Your measure of success is in seeing that the URLs that you do want to be indexed do get indexed, and that they are no longer tagged as Supplemental, perhaps a few weeks after the fixes are put in place.

Again, you need to look into why a URL is Supplemental, only if that URL returns a "200 OK" response.