Modem lost downstream signal, as you would expect given the extremely low power level.
---------- Post added at 10:29 ---------- Previous post was at 10:18 ----------
Originally Posted by Sephiroth
Sounds like a load of rubbish to me. A "bigger cable"? They would need to ensure that the impedance between your wall box (or indeed your cable modem) and the street box is 75 ohms. So that might require a re-pull of the cable to your wall box thriugh the green pipe you mentioned. They'll use the old cable to pull through the new.
Thicker cable = less attenuation / signal loss so higher power level received on the other end of the cable. This isn't related to impedance at all, all cable VM use is of the correct impedance. Where cable were of an incorrect impedance it'd indicate a fault with the cable which would ideally need replacing. The reported power level is voltage relative to 1mV RMS and impedance doesn't enter into the calculation.
Problem seems to be nothing more interesting than a damaged cable or loose connector, maybe on the outside of probabilities a totally buggered amplifier, hence the >20dBmV variations in power levels.