Issues with Comcast Modem Upgrade- Arris TG862G/CT

After following the steps from Comcast on upgrading my rental modem, I am having issues connecting to the internet; though it says everything is online. Before I list the specs on everything let me say that when I moved into this apartment in March, a Comcast service tech was sent out to hook up the internet/cable. He tried to install the same Arris Modem/Gateway that I just received in the mail, but was having issues and told me to stick with my old one. He stated that I would not have any speed issues with my upgraded service. 

Current Modem:                Scientific Atlanta 2100 

Current Internet:                Blast!

Splitter(s):                           Yes. One(1)

New(upgraded)Modem:  Arris TG862G/CT

I have done a reset, a two(2) minute power down, and also tried hooking up my wireless router to see if it changed anything. No dice with a direct plug or wireless. I swapped it back to the Scientific Atlanta unit and everything is working fine. Any information to point me in the right direction would be great.