Well, the signal levels and SNRs that you modem display all look OK, but the error messages/T3 timeouts in the Event Log indicate an upstream issue of some kind:
From: »
Comcast High Speed Internet FAQ »
What do messages about timeouts mean?quote:
T3 ( Ranging Request Retries Exhausted )
Explanation: The cable modem has sent 16 Ranging Request (RNG-REQ) messages without receiving a Ranging Response (RNG-RSP) message in reply from the CMTS. The cable modem is therefore resetting its cable interface and restarting the registration process. This typically is caused by noise on the upstream that causes the loss of MAC-layer messages. Noise could also lower the signal-to-noise ratio (SNR) on the upstream to a point where the cable modem's power level is insufficient to transmit any messages. If the cable modem cannot raise its upstream transmit power level to a level that allows successful communication within the maximum timeout period, it resets its cable interface and restarts the registration process. This error message is DOCSIS event message is R03.0, Ranging Request.
So the problem could be due to a low upstream SNR (uSNR), or an issue with the node or with that modem.
Try IMing netcool
and see if he will take a look at this to figure out what may be causing them.