Comcast DHCP issues with some Asus routers?

There are several posts in the Comcast forums about users having problems with their Asus routers and Comcast. It will not connect and gives a message that the DHCP is not functioning properly. Some have it fixed by getting the modem properly provisioned, but that doesn't always work.
Has anyone seen this? Any ideas on what is going on? I have a 68U that is working for now, but I'm holding off on any firmware updates, just in case.
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Comcast DHCP issues with some Asus routers?