If you are having constant T4 reboots then this firmware won't likely fix anything for you. I have it and did not do anything for me. It is only meant to fix one of the channels showing up as offline.
What I noticed with my connection is that the upstream signal varies a lot, so once it goes high enough the modem can no longer communicate and will T4. We are talking 6 or 7 dBmV swings from low to high. So if my normal signal is 46dBmV that would be perfectly acceptable, but it fluctuates so much that it will swing up to 51dBmV which is the cutoff for 3 bonded channels.
It's kind of a double hit when you go from 1 upstream to 3. With one upstream the modem can push 57dBmV before it is maxed out, that leaves a lot more headroom. The other thing is that I don't think my modem swings as much with one upstream either. I didn't watch too closely but I would guess it only varies 3dBmV instead of 6.
My solution? »cabletvamps.com/Products/ERA-4100.htm
Someone on the Comcast's forums said they used this amp to fix their issue. I've used their gear before when I had a bunch of TVs so it wasn't that hard of a sell for me. (Electroline makes good gear and the previous item I bought carries a 10 year warranty.)
Basically what the amp does is takes the upstream signal and boost it by 10db. You only want / need this hooked up to the cable modem as you want to avoid picking up as much RF as possible. A good, short RG6 cable from the modem directly into this should keep the amount of ingress down. So now instead of my modem having to push 46dBmV to get a signal back to the CMTS, it only has to push 36dBmV. For normal usage the only thing that does is make it look prettier. But when the signal starts going bad and the modem needs to crank up the power, it has more headroom now. I've seen my modem pushing 46dBmV with the amp in place which means I would need to be up to 56dBmV without it in order to communicate. That would still be within the threshold on a single upstream, but not when you have 3 channels. So the modem is still able to stay online even during those rough times.
I've still had 1 T4 since I put the amp in place. It could be the SNR was just too low or maybe there was a short power outage causing the amp to turn off (It's not on my battery backup yet) or maybe even just some work being done at the head end since it was at 1am. But in the past 10 days that is 1 T4 versus a T4 about every 3 hours.
I would suggest just watching your modem and seeing if you notice a pattern like mine. If you do then your options are either get an amp, or get a docsis 2.0 modem so they can't give you upstream bonded channels. I should point out as well that if you do have a bad drop, splitter, etc that using the amp wouldn't make sense until you have those issues fixed. In my case I had a perfectly working connection until July on a drop that is about 1 year old now and has 1 good splitter on it. There really isn't anything I can do to improve my signal levels as the connections are already solid. Also RG6 vs RG11 makes little difference for low frequencies to having the drop replaced with better cable wouldn't really help. 2 months of posting in Comcast Direct didn't make a difference either, but you might have better luck than I did.