UPDATE: Looks like the DNS issue is starting to get resolved. The fix may not have fully propagated yet.
If your Akismet Spam Filtering is currently broken, it is probably due to a DNS issue going around. I reported it to the akismet mailing list and found that people all over the world are having the same issue. It is not just a Comcast issue.
The temporary fix is to add the following entry into your hosts file:
Hopefully the Akismet team will fix this problem shortly.