[CentOS] New Install for 6to4 tunnel

Folks

It appears that Comcast is using 6to4 tunnelling on all new installs 
in Washington and Oregon.  I am trying to install Centos 6 (latest), 
and nothing I do seems to work.

My method is as follows:

The Comcast modem is directly connected to the box.
Insert the NetInstall disk and bootstrap.

Select the URL method of install, and enable both IPV4 and IPV6.  I 
know that if I enable IPV4 only, it fails.

Network manager never manages to initialize the network.

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As a sanity test, I took a functioning Windows 7 laptop, plugged it 
into the Comcast Modem, and the connection came up and worked.  I had 
both an IPV4 address (globally routable, likely dynamic) and an IPV6 
address.  I know therefore that the modem, and cable all work.

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Is Linux installable on such a network?  It installs elegantly and 
effortlessly in an IPV4 environment.  It appears that there will be a 
growing number of 6to4 tunnel environments as the world slowly moves 
to an IPV6-only protocol.

Advice please?

David