Periodic Cable Modem Routing Issues

The Issue

A few times now, and today in particular, the comcast modem seems to stop being able to route to it's first hop (the gateway).    If I do nothing it will recover but then the issue will reoccur approximately every four minutes until I power cycle the modem.

(NOTE: My procedure for power cycle is to unplug the power for 1 minute and reconnect.)

When it's in this state:

1. The administrative interface shows everything connected and locked.

2. Web interface adminstrative tool pings to the gateway will fail.   This is clearly an issue with the cable modem and not other LAN equipment.

Cable Modem: SMC Networks SMCD3GCCR

Firmware: v3.1.6.54

Routing Gateway: 73.98.96.1

If I power cycle the modem, it will reconnect and be fine for an indeterminate period of time (hours, days, weeks).

My Questions:

1. Is this an issue with this make/model of cablemodem?

2. Is this an issue with this firmware version?

3. Is there an issue on the Comcast side (the gateway or elements thereof)? 

(I don't think this is worth a location service call at this time as I am not convinced this is a local issue at this point due to the incredibly variable time frames.)