I also have Comcast and what I've noticed is their SMTP server is sometimes busy, even when I use Thunderbird as my email client on Win 7 and 8. Typically it takes me 20-30 seconds just for TB to log on to the SMTP server when I send an email. Your SMTP log says "operation timed out" and this would be consistent with Comcast SMTP servers. Try again in a few hours.

Do you still have the problem? Also check that you are using the right port. I think they use a different port to prevent spam.

Also increase your timeout to 60 seconds.