constant network drops

Using comcast with a fairly new surfboard sb6121 modem, and a wrt320n router.
Probably about 3-5 times per day, the network will drop.  
Waiting a few moments, or renewing the address from the router (which is probably just a timing issue resolved by the wait) will allow the service to be restored.
However, I'd like to know what's causing these frequent resets.  

This is the log from the modem yesterday shortly after it occured.  Is there any indication what the trouble is?  How else can we sort this?

Sep 02 2013 19:27:40	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:23	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13	6-Notice	N/A	Cable Modem Reboot due to T4 timeout ;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 19:26:48	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 19:26:18	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 17:59:07	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:19	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13	6-Notice	N/A	Cable Modem Reboot due to T4 timeout ;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 17:58:13	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 17:44:26	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 17:15:48	3-Critical	T05.0	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 17:13:35	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 16:26:04	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:20	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13	6-Notice	N/A	Cable Modem Reboot due to T4 timeout ;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 16:25:10	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 16:22:25	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:22	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13	6-Notice	N/A	Cable Modem Reboot due to T4 timeout ;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Sep 02 2013 16:21:35	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=6d:ce:a3:e3:a1:50;CMTS-MAC=00:02:4e:31:42:18;CM-QOS=1.1;CM-VER=3.0;

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sirbountyAsked:
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Steven CarnahanNetwork ManagerCommented:
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jhyieslaCommented:
We had a similar issue, at least as far as network drops and the modem resetting. I opted firstly to change the modem, but that didn't seem to solve it.  So I called Comcast and they came out and determined that I had a bad line from the outside box to my cable modem. They replaced it and I think I've only had one drop in the last couple of months.

If you do call them and assuming that Comcast where you are is the same as where I am, and if the trouble is found to be with inside wiring, you will be dinged for a $60 service call unless you have their special support feature that costs me about $4/month.
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sirbountyAuthor Commented:
They've replaced the line once in the past - said squirrels were eating through the cabling to get at the filament.  Supposedly put in a thicker cable and that was supposed to resolve it...
So, nothing showing up very clear in the log info?
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Steven CarnahanNetwork ManagerCommented:
In reading through the thread I pointed at I see the same information that is in your log.  It seems that it is probably exactly what jhyiesla has mentioned however they did look at other stuff.
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jhyieslaCommented:
And it may not be outside... could be something with the inside wiring or you might even need some amplifier on the line?  Comcast should be able to determine that, but I've seen one guy come in and say this is what you need and a year or two later someone else come in and wonder what the first guy was doing :)
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