We're not aware of any issues with Comcast routers.
When you're setting up the network on the chumby, at some point, it will show the MAC address of your chumby device.
Can you check to make sure the Mac is *not* 00:00:00:00:00:00? if it is, then your network adapter probably came loose.
Chances are the spell checker for your computer does not understand the word "chumby" - the forum doesn't do any spellchecking. You can probably add "chumby" to your "accept" list on your computer - for instance, on a Mac, you can add new words to the file ~/Library/Spelling/LocalDictionary (they must be in alphabetical order).