said by mclasser:
I was wondering what such a timeout meant.
The T4 timer is incremented when the cable modem doesn't receive a downstream ranging opportunity. The CMTS is required to send a ranging response "answer" to the cable modem with "T4" seconds (T4 is a configurable value)...if the cable modem fails to hear back from the CMTS within that amount of time will go ahead and reinitialize.
This is usually caused by noise, but in your instance since it happened only once and during a maintenance window your hypothesis that it was maintenance related is sound.