I found this forum when researching my sudden slow internet speeds. We have had Comcast for about 5 months and it has worked very well up until this week. I have noticed a drastic slowdown of file downloads for work, downloading video's on YouTube and just general browsing. I'm not very computer savy but would appreciate any help you could give me to figure out what is going on.
The modem's upstream power level would be considered to be a bit low for a 64 QAM return carrier. Somewhere in the 40dB to 50 dB is recommended in most systems that use this modulation scheme. Perhaps you should book a tech to investigate and correct.