frequent connection drops

For the last few weeks, my connection has been dropping multiple times every day. My SB6141 cable modem reboots and reconnects very quickly, always less than 2 minutes. Here are the log messages from the latest reboot:

Jan 15 2014 16:23:39 No Ranging Response received - T3 time-out
Jan 15 2014 16:23:39 Ranging Request Retries exhausted
Jan 15 2014 16:23:39 Unicast Maintenance Ranging attempted - No response - Retries exhausted
Jan 15 2014 16:23:48 No Ranging Response received - T3 time-out
Jan 15 2014 16:23:48 Ranging Request Retries exhausted
Jan 15 2014 16:23:48 Unicast Maintenance Ranging attempted - No response - Retries exhausted
Jan 15 2014 16:23:53 No Ranging Response received - T3 time-out
Jan 15 2014 16:23:54 Ranging Request Retries exhausted
Jan 15 2014 16:23:54 Unicast Maintenance Ranging attempted - No response - Retries exhausted
Jan 15 2014 16:23:54 No Ranging Response received - T3 time-out
Jan 01 1970 00:00:14 Cable Modem Reboot due to T4 timeout
Jan 01 1970 00:00:29 No Ranging Response received - T3 time-out
Jan 01 1970 00:00:41 ToD request sent - No Response received
Jan 15 2014 16:24:52 MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1
Jan 15 2014 16:24:52 TLV-11 - unrecognized OID

My signal seems OK. The downstream power is 1-2 dBmV on all 8 channels. Downstream SNR is between 35-38 dB. Upstream power is 41-44 dBmV on 3 channels. The cable modem is on the only line coming into the house. The box outside the house has a 2-way splitter with the other "out" leg terminated.

While I have a connection, everything works properly and fast. It just dies way too frequently.

Anyone have any ideas what the problem could be?