Comcast XFINITY → [Connectivity] 3rd week of problems, 2 tech visits, service stil

first, the specs:

Modem - Motorola SB4100 cable modem
Software Version - SB4100-1.4.9.0-SCM00-NOSH
Network setup - nVidia nForce network adapter (onboard)* to modem to signal, no router/hubs
*although the problem also occurs on a linksys NIC signal is split once for cable television, work performed by comcast tech.
Firewall / AVS - Windows Firewall default configuration with ICMP allow incoming echo request enabled to allow remote ping logging of my deault gateway. No AVS enabled.

Been having intermittent connectivity for several weeks in Vancouver, Washington, multiple calls to Comcast and 2 visits from service techs have failed to resolve the issue. First visit, the problem was present using both my own modem and a test modem the tech had. After the tech made several calls to the service center the problem just went away. connectivity was restored on the test modem and my modem. Problem diagnosed as "Line problem".
Second visit happened while connectivity was restored, "No problem found".... yet it continues.
I have noticed a pattern of service dropping every morning after midnight and continuing for several hours, although the problem isn't exclusive to this timeframe. When connectivity is lost, the modem doesn't appear to lose sync (4 steady green lights and one flashing yellow) but it will fail to re-sync after a powercycle. The following is a sample of attempts to ping the default gateway just prior to powercycle (ip has been edited form actual pinged address, all other data retained):

Request timed out.
Request timed out.
Reply from 12.34.567.1: bytes=32 time=22ms TTL=64
Reply from 12.34.567.1: bytes=32 time=24ms TTL=64
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Reply from 12.34.567.1: bytes=32 time=9ms TTL=64
Request timed out.
Reply from 12.34.567.1: bytes=32 time=22ms TTL=64
Request timed out.
Request timed out.

The following is a picture of a graph generated by smokeping for the last 48 hours or so:
»img102.imageshack.us/img ··· y4oh.jpg

current SNR is 38dB

This seems like it shouldn't be hard for Comcast to track down. I can pretty much say with confidence that the issue will return tonight, if not sooner. what other tests can I do before/during/after connection loss to help narrow down this problem? Any help is greatly appreciated.

change the modem:)...
My boss's internet was just like that.. i changed the modem and BAM WORKS perfect

does seem like a lot of people with sb4100 that have problems anymore. test modems are usually recycled junk.

1. The test modem was an sb5100
2. You're implying that both modems were bad, then simultaneously fixed themselves.
3. How does a bad modem explain the consistent early morning drops?
4. Even the service techs didn't think it was the modem.

no what im saying is alot of people have been having problems with the 4100. test modems are nothing but used modems and anything goes with them.

You could identify whether the packet loss is upstream or downstream. The way I know to do this is to talk via a VOIP application such as Skype to somebody without that problem. See which way the voice drops or garbles.

Actually, it did occur once while using ventrilo, although it didn't really reveal anything. From my end, it just sounded like there was a pause in the conversation prior to losing connection. The loss continued for several hours, preventing me from asking anyone who was on what they may or may not have heard.
The first tech said the problem was in the upstream based on tests he made prior to the problem solving itself.
I'm not sure, but i think the grey bands on the smokeping graph show whether a problem is upstream or downstream, depending on which side of the median line they appear... not sure on this though.
I know the colored centerline represents packet loss.

smokeping data for the past 3 days or so. there's a definite pattern forming. also note average and current packetloss.