Sounds like you have a low signal at the tap, I would NEVER go from Comcast to DSL. I would check your higher channels on your TV and see how the picture is , then check your lower ones as well . What type of coax do you have ? How many splitters ? Do you have a amplifier ? as far as your modems being replaced , whoever is replacing them are idiots because they dont normally " GO BAD" Once the modem has a QOS "quality of service" Then it goes through a REG-RSP Registration and once that passes the modem comes online.
First check your coax
try to get the modem as close as you can to the outside connection, and getting a amplifier "can" help but if you plan to get one from Radio Shack forget it . If you need one PM me I have around 60 of them
Your DHCP release is because your running the cheap service , I will use this as a example d11_m_sb5120_silver_c01.cm
Now if you was running a better service you wouldn't have a renew / release d10_m_ubr905_ccowps_c05.cm
