See if COMCAST has a support section on their website. If they do see if it has Known Issues or simular name and click on it. The problem could be on their end as easilly as yours. If you got the same frontal system we did the winds been murder the past 24 hours or more here. Most services have a section where they post any known service issues on their end.
I need to rule out the possibility of a virus, which is what I personally think it is. The situation has been worsening over the past month and appears exclusive to browsing (not weather related).