Cannot login to admin with www.domain.org site. Special case?

Hello!

I was asked to update a client site on my network from "plain" zetapsi.org to http://www.zetapsi.org. Their DNS admin updated their DNS so that zetapsi.org redirects to http://www.zetapsi.org, as you can see.

Network Domain Options are "mapped domain" for both.

I removed the Domain Mapping plugin entry for zetapsi.org and left in http://www.zetapsi.org. I reviewed the sites options for any non-www references.

In Firefox (Win), I can log in to the administration area.

For other browsers (IE, Chrome), when I log in to http://www.zetapsi.org/wp-admin, there is no admin bar and no code in source showing I'm logged in. It's an admin/administration login loop!

To test, I added the domain zetapsi.empathik.org to the Domain Mapping plugin, and logged in that way, I and was able to successfully see the admin area.

While in Firefox, the zetapsi.org Domain Mapping settings are the following (and are confirmed in phpMyAdmin table _domain_mapping) :

Custom Domain Original Blog Address
http://www.zetapsi.org/ http://www.zetapsi.org/
http://zetapsi.empathik.org/ http://www.zetapsi.org/

Resetting to "original domain" or "domain entered by user" create the same results.

Is the www a special case? Am I missing something in the config? DNS settings? Magic wand? Bad mojo?

Please note, I've been flushing all browser data throughout the above.

Thanks.