Navy....
Your UPstream level is WAY high...right at the "break-off" point to sync loss......UPstream power should normal in the upper-30s to upper 40s, with anything over 50 considered suspect...
BTW....Your SNR is right at the "edge" for QAM256, too.....33dB is considered MINIMUM for the new architecture...SNR much below 30dB could start your modem randomly rebooting, trying to find a good signal.....Have you checked ALL your coax connections - inside and OUT? Are they all clean, tight and DRY? Same with all coax runs....any splits, cracks, sharp bends/kinks/pinches? If you come through the "inspection" clean, you probably should call Comcast and have them come out and do a COMPLETE signal/noise level check....and be sure to have the tech report the numbers he/she finds back to YOU prior to leaving the site...Good luck!