The event list suggests that you have an upstream problem. There is instability and the incrementing power levels confirm this.
if the modem is struggling to communicate with the CMTS, then the power output is stepped up until the CMTS can read a sensible signal. If it can't, you'll get timed out or switched to another upstream channel.
VM's tech support could ascertain what's happenig by examining the CMTS "flap list". You can Google the terms I've used if you don't fully understand all this weird stand. A good definition of the flap list is at:
http://www.juniper.net/techpubs/soft...shooting3.html