In case this ever happens to you again...
I have gmail and comcast. For about a week, I was unable to login to gmail at home. I went to
www.gmailforums.com and found that this was a fairly common problem for people with wireless routers. Turned out all I had to do was a power cycle, and I was back in business! Apparently gmail randomly bans IP addresses (maybe those on wireless routers, for security reasons?), and doing a power cycle will give you an IP address.
Something like that.