To isolate the issue, connect any device directly and monitor the connection for 24 hours. If the internet still drops, we would suggest checking the cable signal levels. A cable signal level refers to the strength and quality of the signal that travels through the coaxial cable to provide your internet service.

Please refer to the link below on how to check the cable signal levels.

http://arris.force.com/consumers/articles/General_FAQs/S33-Cable-Signal-Levels

To understand you better, are you trying to use both Ethernet ports on the S33, and do you have a router connected to the modem already?

The issue seems to have been a bad cable line from the pole to the line coming to the house. Cable was replaced by cable company after they tried to tell me it was the modem. I was able to us the data from the modem to give clear indication it was not the modem. I got them to give me a credit for 1 day service and I indicated I would call every day until the problem was fixed. 
Watching the Event Log on the modem I also now see, for approx 24 hours, there have been no sync issues and no other errors (prior events were type 16 and type 24 as well as MDD message timeouts. The only indication in the index is me logging in multiple times. So, seems problem solved by cable company fixing their line.

Just checked again and now see MDD message timeout ; then an event Type Code 4 approx 6 minutes ago. Will watch for another 24 hours.