What helped me with this a while back was to reset my modem BUT instead of just unplugging or shutting off the modem with the on/off button, I unplugged the coaxial cable from the modem as well. I was skeptical when a support tech told me to do that (no one had ever told me to do it before), but doing that additional step made all the difference.
(The support tech was from Comcast not eBay, just to clarify)
