Chances are you're in a DUL/dynamic list on SORBS or another service. What you need to do is work your way up past the first level grunt at Comcrap and speak to an actual engineer, and they need to submit updated lists of dynamic vs. static IP lists to the various blacklists and also key email providers (gmail, yahoo, notHotmail, etc.) and other providers (time warner, etc.) so that they acknowledge your block as a static block of IPs.
What happened is some grunt at Comcast probably fat-fingered when updating these lists.