I'm finding this issue to be computer related vs user related. I can have the same user on two computers and one with authenticate and the other won't.
In addition, I have found that the "connect to outlook" choice on the sharepoint site also dissapears on the problem computer(s)
If you call into tech support, ask for a level 2 support agent. You may get lucky on reach someone who knows sharepoint
Time to vent:
If Comcast want to offer "business class" tools such as sharepoint, they should do two things:
1) have people who are easy to reach that know the product
2) Time to catch up on technology. Sharepoint 2007 has always been marginal. Sharepoint 2013 works so much better
maybe Office365 is a better choice