SEOMoz Crawl Diagnostic indicates duplicate page content for home page?

[Linesides]

My first SEOMoz Crawl Diagnostic report for my website indicates duplicate page content for my home page. It lists the home page URL Page Title and URL twice.

How do I go about diagnosing this?

Is the problem related to the following code that is in my .htaccess file? (The purpose of the code was to redirect any non "www" backlink referrals to the "www" version of the domain.)

RewriteCond %{HTTP_HOST} ^whatever.com [NC]
RewriteRule ^(.*)$ http://www.whatever.com/$1 [L,R=301]

Should I get rid of the "http" reference in the second line?

Related to this is a notice in the "Crawl Notices Found" -- "301 Permanent redirect" which shows my home page title as "http://whatever.com" and shows the redirect address as http://http://www.whatever.com/

I'm guessing this problem is again related to the redirect code I'm using.

Also...

The report indicates duplicate content for those links that have different parameters added to the URL i.e. http://www.whatever.com?marker=Blah Blah&markerzoom=13

If I set up a canonical reference for the page, will this fix this?

Thank you.

[KeriMorgret]

Hi Perry,

In your browser, are you seeing things redirect to the double http? I think there's a bug in the crawl tools that's causing some false errors right now. Before you go work on the redirect file, could you send an email to help@seomoz.org to first make sure we're not the ones that messed up?

Thanks!

[Linesides]

I contacted the help desk as instructed an was told:

"I took a look at the campaign and it looks like our crawler can't parse the 301 redirect you have in place on the main page. The reason for this is the redirect in place, adds two https when rogerbot tries to crawl through it. Roger can’t parse the redirect as is, but it can identify it (as it did in your notice’s report on the crawl diagnostics page). This isn't a problem for browsers since they are made to ignore redirects of this nature. Crawlers on the other hand have a strict code to follow and can't follow redirects like that. When I load up your site [mywebsite.com] right now, it redirects to www.[mywebsite].com. Try creating a new campaign under the domain you are redirecting to, this should clear any issues up."

And so I did that and it looks like that worked after the new crawl, however I then set up another campaign for another website I manage being sure to use the "www" in front of the domain and got the same problem again -- the home page appears twice as duplicate content.

So I'm back to asking my primary question again: What is the definitive redirect code to use to convert a non "www" request to a "www" request? The same redirect code mentioned in my first post is being used on all of my sites.