What region are you located?
Is there any user information in the User Manual regarding the Setup of IPv6?
I attempted to download the User Manual from the UK web site however I see that the manual is corrupt. Is the manual on the CD?
Usually by just enabling IPv6 options on the modem should turn it on. I presume there are other IPv6 options like 6to4, 6rd, or Local Connection only?
Be aware that this model has been phased out, at least on the UK site.